Babylon 5 is a multi-Emmy Award winning and nominated American science fiction television series created and produced by J. Michael Straczynski for Warner Bros. While preceding it in development by half a decade, it was produced and aired at the same time as Star Trek: Deep Space Nine, resulting in back and forth accusations of plagiarism, which led to a fierce competition between the two franchises at the time.
The primary series ran from 26 January 1994 to 25 November 1998 after its pilot episode was broadcast on 22 February 1993. It was the first truly successful American futuristic, modern space-oriented science fiction television series outside Star Trek and therefore the first serious contender with the Star Trek franchise, which until then had pretty much the run of the science fiction television landscape since it had been relaunched in 1987 with Star Trek: The Next Generation. Like Star Trek, there have been several attempts to create viable spinoff properties, including six made-for-TV movies and the short-lived series Crusade, featuring Daniel Dae Kim, Marjean Holden, and Tracy Scoggins.
Enjoying a considerable measure of success while the original five-season source series was being produced and aired, firstly on PTEN (seasons 1-4) and subsequently on TNT (season 5), the franchise eventually faded into obscurity due to a combination of intentional sabotage by TNT, poorly considered money-saving maneuvers by Warner Bros. (including, but not limited to, the decision to save $5,000 per episode which in the process made it also impossible to produce a later high definition version of the show with recomposited wide-screen versions of effects shots, after digital assets were lost as the studio was unwilling to pay for their upkeep), as well as internal studio politics. Incidentally, the television division of Warner Bros., which produced the show, was at the time headed by Les Moonves, an executive not known for his affinity for science fiction in general and Star Trek in particular;  Moonves left his mark on Star Trek later on, rarely in a beneficial manner, and, according to Straczynski, having already done so for Babylon 5. 
The series was widely acclaimed for its ambitious writing, much of it by Straczynski himself, who endeavored to tell a complex, predetermined epic story arc, in the form of the Shadow War(s), over the series' entire run, as opposed to the episodic or two-part story format until then employed for science fiction television series. It thereby convincingly dispelled the widely held belief by Hollywood studios that television audiences lacked the attention span to remain interested in a science fiction series format thus conceived – or in any other serialized television programming with complex storytelling for that matter. (see also in this regard: Battlestar Galactica: Reception and demise)
While the show continues to be available on Standard Definition DVD and still has a cult following, albeit dwindling,  it has neither been broadcast nor streamed in syndication since the early 2000s however, making it hard for potential fans to discover and preventing a fan driven comeback such as was enjoyed by Star Trek.
In the end, the live-action Babylon 5 franchise encompassed at the end of its fourteen-year lifespan,
J. Michael Straczynski began working on the Babylon 5 concept in 1986.  In 1987, he began pitching it, with a script for the pilot and conceptual artwork, to Hollywood executives.  He pitched the program (with pilot script, artwork, series bible, character descriptions, and synopses for approximately twenty-two episodes) to Paramount executives in 1989.  The series was greenlit by Warner Bros. in November 1991.  Warner Bros. was one of the Hollywood studios that became increasingly envious of Paramount for its Star Trek property due to the growing profitable and stable revenue stream stemming from that franchise, especially in the early-1990s when TNG was soaring in popularity, becoming one of Paramount's most profitable properties in that period of time, and Warner was actually one of the very first studios to act upon the desire. Up until that point in time The Next Generation had for almost a decade been the only new (successful) science fiction show being aired on television, when discounting the syndicated reruns of older shows, most conspicuously Star Trek: The Original Series. (A Vision of the Future - Star Trek: Voyager, pp. 50-51)
Actually, Brandon Tartikoff, then newly-appointed Paramount Pictures chairman, asked Rick Berman in 1991 to develop a new Star Trek television series in order to further capitalize on the success of their franchise. Next Generation showrunners Berman and Michael Piller discussed plans for the new series with Gene Roddenberry prior to his death in October 1991. Star Trek: Deep Space Nine was officially greenlit in January 1992.  Filming on the Babylon 5 pilot, The Gathering, was completed before filming began on Deep Space Nine's pilot, "Emissary", but Babylon 5's post-production took longer (unsurprisingly perhaps, as the new show did not have the well-oiled post-production process Star Trek had in place yet, especially in the light of their heavy reliance on the then-newfangled CGI techniques), so "Emissary" aired on 3 January 1993 and The Gathering aired seven weeks later, on 22 February.
Premise and storylines
Straczynski has suggested that Paramount TV development executives may have "guided" the development of Deep Space Nine with the intention of co-opting Babylon 5.  He has, however, been careful to point out that he does not believe that Berman or Piller were aware of the Babylon 5 concept when they were developing Deep Space Nine, or that they deliberately ripped off Babylon 5.  Nonetheless, if Straczynski had been right in his unspoken suspicions, it would have constituted a case of history repeating itself, but then with Star Trek on the receiving end; in April 1964 Gene Roddenberry and Oscar Katz presented the Star Trek is... pitch to television studio CBS, which was rejected by them, but not before having been thoroughly questioned about it. It turned out that CBS had its own science fiction show, Lost in Space (in which a young Bill Mumy played one of the primary characters – making him an alumnus of four successful science-fiction franchises as he also made appearances in The Twilight Zone), under development at that time, and both Katz and Roddenberry in particular were convinced that CBS had picked their brains. (Star Trek Creator: The Authorized Biography of Gene Roddenberry) Like Deep Space Nine and Babylon 5 would become in theirs, Star Trek: The Original Series and Lost in Space became science fiction franchise contenders in their day, with the latter then actually perceived as the more successful one while both were originally aired.
Despite his diplomatic stance however, Straczynski could not refrain from pointing out a number of similarities between Babylon 5 and Deep Space Nine, particularly their respective pilot episodes:
Straczynski also commented on what he perceived to be similarities in set and prosthetic designs, as well as the notion – mentioned in Deep Space Nine publicity but rarely acknowledged directly in the program itself – that the holosuites in Quark's would act as a virtual bordello.  In 1993, Straczynski noted a striking similarity between the just-aired Deep Space Nine episode "The Homecoming", in which Quark is branded on the head by the xenophobic and radical Circle, and the Babylon 5 episode "The War Prayer" (then in post-production), in which a Minbari is branded on the head by the xenophobic and radical Homeguard; he emphasized that no one on the Babylon 5 staff knew of the DS9 plot point until "The Homecoming" aired, by which point filming on "The War Prayer" had been completed. 
Later, in 1996, Straczynski said:
"Sometimes it does bother me, and I wonder about what the heck's going on, when I see the only other space station series doing a big arc about alien forces infiltrating Earth government, and brewing civil war on Earth, at the *exact same moment* that we're doing it on our show; earlier, later, fine, but that they'd do basically the same thing at the same time feels like another attempt to co-opt what we're doing on this show. (Not copy; co-opt, which happens all the time. ....) If you kinda know the direction someone else is going, you try to jump ahead and get there first, so that the other either loses impact, or is considered simply an imitation. (Which is one reason why DS9 was hurried through post production to get it on the air a few weeks before B5's pilot, I suspect.)
Are we being co-opted? I dunno. When I hear that there's a red-headed woman character on DS9 named Leeta (pronounced the same as Lyta); when I see them doing the same kind of arc we're doing but getting it out a little earlier, I will confess it does give me pause sometimes. I try to think the best under these conditions. For now, I'm asuming [sic] it's all just coincidence."
After seeing "Homefront" and "Paradise Lost", Straczynski recognized that the story was an homage to the film Seven Days in May, implicitly withdrawing this criticism. 
In the face of the rivalry, Majel Barrett-Roddenberry agreed to a guest appearance on Babylon 5 as a gesture of goodwill to encourage a reconciliation between the fandoms.  She played a widow of the late Centauri Emperor, whose greatness and vision for peace had not been fully appreciated within his own lifetime. She foresaw Ambassador Mollari's rise to power.
Aside from Straczynski's own observations, it should also be noted that Deep Space Nine too adopted a long, multi-season story arc from the third season onward in the form of events surrounding the Dominion War. The Star Trek franchise later repeated this to a lesser extent for the third season of Star Trek: Enterprise in the form of the Xindi threat story arc, and the Federation-Klingon War story arc, featured in the first season of Star Trek: Discovery. In the 2019 Star Trek documentaryWhat We Left Behind though, later Deep Space Nine showrunner Ira Steven Behr claimed full credit for his show being the "inventor" of the multi-episode/season story-arc format in the 1990s television landscape, which was a demonstrable falsehood – if only because the 1980s drama series Dallas for example, consisted of one long story-arc, albeit a non-complex, simple one.
Another thread running throughout Babylon 5 right from the start, was the presence of a secretive organization with considerable military capabilities embedded within its Earth Alliance organization that pursued its own agenda, called Psi Corps. One of its main recurrent operatives, Alfred Bester, was played by Star Trek alumnus Walter Koenig. The notion of secretive paramilitary organizations pursuing their own agenda was adopted by Deep Space Nine as well, not only once, but twice, with the introduction of the CardassianObsidian Order and Starfleet's Section 31 in the series' second and sixth season. William Sadler played the recurrent Section 31 operative Luther Sloan, a role comparable to the one Koenig played on Babylon 5. Nonetheless, it should concurrently be noted that a similar Romulan organization, the Tal Shiar, was established the same month the Babylon 5 pilot aired in the Next Generation episode "Face of the Enemy" which aired on 8 February 1993, fourteen days before the Babylon 5 pilot, though this had more than likely been a case of coincidence considering their near simultaneous airings. Section 31 was further explored by the Star Trek franchise with later reappearances in Star Trek: Enterprise, Star Trek Into Darkness, and Star Trek: Discovery, and is currently slated to become the subject of its own spin-off series in 2020.
In service of Straczynski's goal of telling a complex, predetermined epic story arc, the show adopted an innovative visual style, taking advantage of advances in computer animation to create for the times spectacular visual effects (VFX) on an economical budget, most notably computer generated imagery (CGI) as pioneered by the show's digital VFX vendor Foundation Imaging, who also provided VFX for the Star Trek franchise later on. The predominant use of CGI in the Babylon 5 was a breakthrough in creating VFX for television, much as the movie Jurassic Park had been for cinema; it went on to become the primary VFX technique.
Despite the signature importance which effects house Foundation Imagining had had for Babylon 5, the company was due to the above-mentioned unsavory studio politics let go from the production after its third season in 1995, leaving the company in dire straits. Yet, the services of the company were picked up the same year by the Star Trek franchise for their production Star Trek: Voyager, after its CGI vendor Amblin Imaging went defunct. It was actually Voyager's VFX Supervisor Mitch Suskin who brought the company to the attention of the franchise; Suskin had served in a similar function at Foundation on Babylon 5, but had made the switch to Star Trek one year before Foundation was let go from the production. However there was an initial trepidation to do so, as Foundation's visual style was so associated with that of Babylon 5. (The Official Star Trek: Voyager Magazine issue 16, p. 35) In this regard David Livingston has observed, commenting on the use of computer-generated imagery in "Explorers", "We were reluctant to do computer graphics, but Peter Lauritson finally came around. He recognized how valuable it is. You can do more stuff with the ship, but you have to do it right. Not to pick on other shows, but Babylon 5 looks like computer-generated imagery. On Voyager and Deep Space Nine, you may not know some of these shots are not motion-control shots. They're really, really good if done properly. You have to spend a couple of extra bucks and get really good artists, but CGI just allows you to do more and you can build more elements into the shots". (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages)
Additionally, Deep Space Nine Visual Effects Supervisor Gary Hutzel has stated, "My particular focus for our show, for Star Trek: Deep Space Nine, is that it should be a visual effects leader; we should never follow, we should never do what's been done before. CGI has certainly been used to various different degrees of success on Star Trek: Voyager, but I think it's still a hit-and-miss prospect, so I'm not interested in doing it." (Star Trek Monthly issue 31, p. 26) Still, Foundation amply proved their mettle for Star Trek, even increasingly providing effects for Deep Space Nine's last two seasons as well, continuing to do so for the first season of Enterprise. Nonetheless, some Babylon 5 influences crept into the designs of some of the ships featured in Voyager; the designs of the Species 8472 bio-ship and Krenim weapon ship for example, echoed those of the Vorlon ships and the titular Babylon 5 station respectively, unsurprisingly perhaps, as these were (co-)designed by Steve Burg and Foundation CEO Ron Thornton respectively for either production.
Another production company of note was the prosthetics and makeup special effects (SFX) company Optic Nerve Studios, Inc., which was contracted in 1993 to serve the original Babylon 5 series. Turning out to be a fruitful collaboration, winning the franchise several Emmy Award nominations and wins in the various makeup categories and therefore putting the novice company firmly on the map in the industry, the company was retained for the remainder of the entire run of the franchise. Restructured into Alchemy Studios by its then owners Glenn Hetrick (who himself had worked as an industry novice on the tailend of the Babylon 5 franchise while employed by the company) and Neville Page, the company was in 2017 contracted for similar services on Star Trek: Discovery (incidentally, launched under the auspices of Les Moonves, until 2019 the head of CBS Corporation), for the re-imagined Klingons in particular, likewise winning the series its first 2018 makeup Emmy Award nomination.
Even though Babylon 5 has somewhat receded in the consciousness of science fiction fans, Star Trek's then-owner, CBS Studios (or rather CBS Corporation), has not been able to refrain themselves of reminding television audiences of the fierce competition that existed at the time between the two franchise, or let the issue slide. In their hugely popular (and Star Trek friendly) sitcom series The Big Bang Theory, series regular Sheldon Cooper occasionally expresses his deep disdain for Babylon 5, while his roommate Leonard Hofstadter loves the series, yet losing each and every argument they have over the series. His most outspoken criticism was voiced in that series' third season episode "The Large Hadron Collision" (S03E15, 2010), where he stated that Babylon 5 "(...)failed as drama, science fiction and is hopelessly derivative", referring to the battle that raged at the time between that series and Deep Space Nine – and, as proxy for CBS, in the process implicitly accusing Babylon 5 of plagiarizing Deep Space Nine. In the later "The Hawking Excitation" episode (S05E21), it was also divulged that Sheldon had begged TNT up to three times to cancel Babylon 5. The stance taken in The Big Bang Theory has irked what remained of the still existing Babylon 5 fanbase, but has also enticed some science fiction fans, new to the series, to check out the series for themselves, because of Sheldon's/CBS's aversion.  Ironically, The Big Bang Theory was produced for CBS by Warner Bros., the former Babylon 5 production company.
Even though several other contemporary television shows were mentioned by Ira Steven Behr in his 2019 What We Left Behind documentary, no mention of the then-serious genre contender Babylon 5 was made in the two-hour long documentary.
As for the Babylon 5 creator himself, according to a news notice in the June 1999 issue of the German Star Trek magazine Trekworld, Paramount Pictures had offered Straczynski a chance to work on the Star Trek franchise but he refused because he didn't want to work on someone else's series and was of the belief that Trekkies had no love lost for him. However, this belief did not prevent him to later work on a treatment for "rebooting" the Star Trek franchise with Dark Skies creator Bryce Zabel in 2004, one that was turned down eventually, as the franchise by that time had decided to run with J.J. Abrams' alternate reality version, which ultimately resulted in the 2009 movie Star Trek. (X)
It is fitting perhaps, that both Deep Space Nine and Babylon 5 will ultimately share a similar fate in that neither are ever likely to see a remastered High Definition release, even though the digital assets of the former are confirmed to be still in existence with the release of What We Left Behind, where remastered snippets were featured. It was the commercial failure of the very expensive 2012-2014 remastered Star Trek: The Next GenerationsBlu-ray releases that makes a HD version of Deep Space Nine (and Voyager for that matter) increasingly implausible with each passing day. Contrary to its onetime franchise competitor however, Deep Space Nine is still being offered, albeit in SD, by streaming services such as CBS All Access and Netflix among others – like Voyager is, incidentally.
Star Trek references in Babylon 5
In the Babylon 5 episode "There All the Honor Lies" (written by Peter David), Commander Ivanova protests an attempt to sell "Babylon 5" merchandise on the station, saying, "We're not some Deep Space franchise – this place is about something!" David expected the line to be cut, but producer Straczynski insisted that it be kept, because it was "fall-down funny." David replied, "You people really ARE dangerous over there, aren't you?" 
In the episode "Voices of Authority", when an Earthgov political representative attempts to seduce Captain Sheridan, Ivanova quips, "Congratulations, captain... I believe you are about to go where everyone has gone before."
A blooper from the episode "Severed Dreams" has Bruce McGill's character, when asked where Robert Foxworth's character General Hague was, say "General Hague... is doing Deep Space Nine. It seems he was double-booked by his agent and nothing could be done." 
Actors who have appeared in Star Trek and Babylon 5
↑Robert Foxworth's characters on Babylon 5 and Deep Space Nine were very similar: both were high-ranking military officers who led coup attempts against civilian governments based on Earth (although the Babylon 5 coup was against a totalitarian regime). Both attempts failed. Foxworth had already been booked for a third appearance as General Hague on Babylon 5 when his agent accepted the Deep Space Nine role, which was filming at the same time. In response, J. Michael Straczynski killed off the character of General Hague off-screen (saying, "Never honk off the writer"). 
↑McGill was cast as a new character to replace the role of General Hague, played by Robert Foxworth, who had opted to appear in a two-part episode Deep Space Nine instead (see above).
Production personnel who have worked on both franchises
Note: Excepting Suskin (who was not employed by Foundation during his Star Trek years), not listed are the staffers of CGI company Foundation Imaging, the vast majority of the original 1993-1995 line-up having also worked on both franchises. See main article for staff listing.