Movies being similar to one another is nothing new. In the earliest days of the medium, studios re-used entire sets, costumes and props from production to production within the same genre. Background players would bring their own gear and getup with them to the lot, hoping to get snapped up for crowd scenes during huge, raucus "cattle calls." The signature "look" of production design or familiarity of formula in a studio's output was considered a feature, not a bug. Few in the target audience for the serial adventures of Flash Gordon and Buck Rogers would complain too loudly that little daylight frequently existed between the two franchises, or pay much mind that dozens of 1950s monster movies were thoroughly interchangeable save for the monsters themselves.
But that was before home video, before 500 cable channels, before digital streaming, and before the fragmenting of the popular culture that has today produced a moviegoing audience that paradoxically demands familiarity and novelty in equal measure: Take what we already love and throw it up onscreen - but make it feel new.
This still isn't that much of an issue for most films. Romantic comedies, slashers and buddy-cop features have been largely interchangeable within their own genre for decades with little complaint from the general audience. But modern superhero movies seem to be held to a different standard, with any minute similarity between this or that character being held up as more evidence that a genre that (however popular) at most manages to put maybe 6-7 entries in theaters a year is somehow entirely too prominent: "Another guy in a cape? Don't we have enough of those?" "He's rich? Isn't Batman rich? So isn't this just Batman again?"
Such talk is sure to kick into high gear now that the entertainment press is set to have two cinematic universes worth of superheroes to kick around, with Batman V Superman: Dawn of Justice primed to introduce Henry Cavill's Superman to all the DC superheroes who were apparently hanging out just offscreen this whole time, and lay the groundwork for them to team up in Justice League. After all, forget having too many superheroes period... do we really need another semi-annual team-up crossover when we've already got The Avengers?
The answer, of course, is no - mainly because we're talking about movies here (and summer blockbusters at that) so "need" is sort of an inappropriate term. But there actually is a good deal of real, substantive difference between The Avengers and the Justice League. Despite the superficial similarities (two teams of superheroes with wildly varied origins and power sets functioning as axis points for their respective shared universes), the groups have historically represented fundamentally different makeups with the potential for fundamentally different stories to be told - it's sort of like asking if there's any real difference between a movie set during World War I versus World War II.
There is, admittedly, a certain level of possibility that Zack Snyder's Justice League movie could end up being little more than character-swapped repeat of Joss Whedon's Avengers. But, in order to do so, he'd have to be ready to massively diverge from over 50+ years of comic history. On the other hand, what makes the comparison a bit on the wonky side is that the Avengers that readers have been able to follow in the comics for the last decade or have very been "Marvel's Justice League" - a who's-who of the publisher's most popular/marketable heavy-hitters, with no less than Spider-Man, Captain America and Wolverine fronting the first lineup of so-called "New Avengers" starting in 2005.
Prior to that, however, The Avengers were something else entirely: A constantly-changing roster of also-rans, C-listers, popular-but-not-Spider-Man-popular mainstays and original (to the book) characters whose offbeat, chaotic existence reflected the anything-goes mindset of Marvel at its best - and the franchise's own foundations.
So goes at least one industry legend, The Avengers were conceived on the fly in 1963 when Stan Lee and Jack Kirby were unable to finish their new team project, The Uncanny X-Men, on time. Owing Marvel Publisher Martin Goodman a team book, they opted to publish a book where a handful of their already-established hero characters (Iron Man, Giant-Man, The Wasp, Thor and The Hulk) teamed up against Thor's troublemaking brother Loki, and decided they should keep hanging out together afterwards. Within one issue, they'd moved into "Avengers Mansion" (an unused extra house belonging to Tony Stark) and had their first major defection (The Hulk, whose life-circumstances didn't really work with a team and whose book was selling just fine on its own.) Within four, they'd made themselves a part of Marvel's long-term history by recruiting the newly-unfrozen Captain America. Twelve issues after that, everyone but Cap quits the team, leaving Steve Rogers to build a new lineup with Hawkeye, Scarlet Witch and Quicksilver - all recently-reformed villains.
It went on like that for 40+ years. Characters would rotate on and off the team more regularly than almost any other ensemble comic, to the point that it often felt as though the only requirements for membership were being not hated too intensely by any of the other members and needing a place to crash for awhile (they got to keep the Mansion even when Iron Man wasn't an active member). The Avengers became a venue for Marvel to give a "push" to new characters they thought had promise, a place to stash characters who needed to be out of their own books for dramatic purposes, and a way for new writers to bring their own favorite characters back under their pen.
It's about as sloppy and haphazard as it sounds, but eventually there was a unique vibe to it that set the tone for the rest of the Marvel line: Despite the ever-changing lineup, The Avengers typically had their own villains and problems to deal with - but the centrality of their presence with the rest of the superhero set (since there was no organizing principal to membership, damn near every hero and definitely every team had a friend, relative or ally who was an Avenger) made them the "hub" of The Marvel Universe. Seldom the top-selling or most talked-about book on the shelf, but always part of the story: All roads led back to The Avengers.
Things couldn't have been more different for Justice League. For one thing, their book happened by mandate and was inspired by legacy. No sooner had DC found success with new incarnations of Golden Age titles like Green Lantern and The Flash than did editors call for the revival of the team-up book concept formerly popularized by The Justice Society of America in the 30s and 40s. But while the JSA had been primarily comprised of mildly-popular second-stringers in its heyday (Batman and Superman, the heaviest hitters in all of comics, were "honorary members" who weren't always involved), the Justice League of America would feature the publisher's most prominent (and most powerful) characters - not as the center of the emergent DC Universe, but as the head. The biggest, most universe-shaking events of the Silver Age DCU tended to flow downward from whatever the JLA were up to. Ironically, that was even true of the competition; Stan Lee and Jack Kirby created The Fantastic Four after Marvel asked them to think up a team of superheroes to compete with Justice League.
If the "structure" of the lives of DC heroes is best understood in terms of the social behaviors of the children they were written for (the Fortress of Solitude and The Batcave are basically the most elaborate treehouses ever built), then nowhere is that more apparent than the way the JLA traditionally ran its business. While The Avengers functioned more like a superhero hostel with a work-for-your-rent program ("We've got beds, but you got to help beat up Immortus at least twice a year"), the Justice League had all of the same level of self-generated pomp and officiality you tend to see from precocious children trying to organize a Very Exclusive Secret Club - think The Little Rascals, but half of them can drop-kick the Moon.
Between roll-calls, membership invites, voting on new prospects (or on who to kick out), scheduled meetings and super-secret handshakes (probably), the JLA sometimes seemed to spend almost as much time on group-management as they did thwarting evil - like the pantheons of ancient deities that they are often compared to, the DC heroes' internal group dynamics had as much effect on their world as their great deeds did. And if you're looking for a core difference between the two teams in terms of what kind of stories they're best suited to tell, there it is: The Avengers are essentially a club of diverse people with a shared hobby, The Justice League are more like mythological demigods united by their very nature. Marvel's team saves the world because it's what most of them do anyway but it's better to do it with your buddies; DC's team does it because they're duty-bound as some of the most powerful/influential beings in their world.
Even though the Avengers of the Marvel Cinematic Universe look more like their post-New Avengers comic selves (no Mansion, not as much "hanging out," more like a strike-team than a club of adventurers) you can see the more classical influence in their united-against-bigger-threats stories and "hub" function within their own world. The solo characters have their own things going on, and what happens in the individual films flows out to the others through the network of their team membership, often creating the bigger problems they need a team to solve in the first place: Captain America and Thor's inaugural adventures sowed the seeds of what Loki did in the first Avengers, which informs Tony Stark's change of viewpoint in Iron Man 3 and S.H.I.E.L.D's ill-conceived actions in The Winter Soldier, which lead directly into the decisions everyone makes in Age of Ultron.
At their core, The Avengers let you tell stories about people setting aside (or not) their own problems in the name of teamwork and the greater good against unimaginable odds, and that's not really a story you can tell with a team featuring Superman, since he is an unimaginable odd. That doesn't, however, mean that making a Justice League movie precludes you from telling compelling stories - it just means you're better off telling different ones. It's difficult (though not impossible) to tell "human" stories with Leaguers because, the way DC frames their heavy-hitters, even the ones who are human... aren't. They're gods, not men, and while that comes with its own disadvantages, it also comes with the benefit of precedent; humanity has been telling stories about gods longer than almost anything else.
The advantage of mythical figures like Zeus or Athena or Odin or Isis - or any of history's other gods, devils, angels and demons - is that they let you tell stories where everything is writ large; where the tangible stakes are as powerful and broadly meaningful as the emotional ones. When a human character suffers emotional devastation it might feel like the end of the world, but when the gods are feeling anxious or insecure the fate of the world can literally hang in the balance. That's the basic appeal of a lot of world mythology, but its often difficult to translate to the screen; with the prospect conjuring memories mainly of aging British character actors bellowing declarative sentences in togas on fog-enshrouded sets. But the decidedly god-like DC super-beings who make up The Justice League, on the other hand? They can allow for stories with same kind of mythic grandeur to be told using characters who, if not necessarily figures of worship, are still pretty damn close.
No, the kind of personal character drama that fuels the quieter moments of the better Avengers-adjacent films aren't a very good fit for most of the DC heroes (even "normal" human Batman is powered by wealth that's barely more conceivable than The Flash's speed), but the Justice League's members can be used to explore big, operatic themes that even The Mighty Thor would sound a bit out of his depth pondering: Wonder Woman, thousands of years old with a firsthand understanding of civilization's progress - and lack thereof. The Flash, who can literally outrun time itself but not his own responsibilities. Aquaman, torn not between two ideals or ideologies but between two entire worlds - one within the other, and ever at odds. Batman, who would represent humanity to the gods even as he has little patience with humans themselves. Superman, who can do anything... but, somehow, not always the right thing.
The unknown quantity, of course, is whether or not the powers behind the planned slate of DCEU movies fully grasps this fundamental property of their characters in order to capitalize on it. The premise of the soon-to-shoot Justice League movie is still unknown, as is the take on each character informing their story. The mega-franchise's kickoff feature, Batman V Superman: Dawn of Justice, has apparently cultivated its approach from deconstructionist takes (Frank Miller's The Dark Knight Returns and the 90s event-comic The Death of Superman), where story existed for the sake of spectacle, not the other way around. It's not impossible to imagine that either the filmmakers, producers or both behind League and it's hoped-for slate of spin-offs have already elected not to aim any higher than "The Avengers, but with the guys we own." But it's just as plausible that the extended development cycle has afforded them the insight to make the opposite decision.
Because while it's probably not the case that Hollywood has run out of room for superheroes, it very likely will run out of room for superheroes who insist on repeating one other. These characters were never built to emulate one another, and it would be a real shame to try and force it on them now.
Batman V Superman: Dawn of Justice will see theatrical release on March 25th, 2016, followed by Suicide Squad on August 5th, 2016; Wonder Woman on June 23rd, 2017; Justice League Part One on November 17th, 2017; The Flash on March 16th, 2018; Aquaman on July 27th, 2018; Shazam on April 5th, 2019; Justice League Part Two on June 14th, 2019; Cyborg on April 3rd, 2020; and Green Lantern Corps. on June 19th, 2020.