The first thought: It’s tricky. Obviously, Marvel has provided a blueprint on how to create a blockbuster film that acts both as a standalone film and as a sequel to numerous other standalone films featuring the origins of the cast of your current movie (so that you don’t have to spend the first ten hours of your two-hour movie just explaining who everyone is.) They’ve shown not just that it can be done, but that you can structure the contracts to retain (almost all of) your cast and have a strong studio involvement to keep things consistent from film to film while still attracting A-list directors with unique personal styles (like Branagh, Joe Johnston and Joss Whedon.) But Marvel had a big advantage that DC doesn’t: They hadn’t made a whole bunch of movies already before coming up with the idea.
DC, on the other hand, has a high-profile Batman trilogy that isn’t even wrapped up yet, one which establishes an internally consistent mythos for the character that doesn’t involve any other superheroes. It’d be difficult to imagine Nolan and Bale’s Batman standing on the same screen with Green Lantern and Superman, even if it seemed likely that Bale would return to the role (which it doesn’t.) They have a Superman franchise whose most recent movie has been more or less entirely disavowed by the studio despite positive reviews and box-office success. And they have a Green Lantern movie that woefully underperformed both financially and critically. The Superman reboot that could serve as the beginning of a hypothetical Justice League launch is coming this year, but it’s anyone’s guess whether Warner Brothers had gotten its act together sufficiently by the time Man of Steel went into production to be able to think of their comics properties in these terms. (I have insisted, and will continue to insist, that the reason Marvel’s films have done so well while DC’s have done so poorly is because Marvel is in a position to be able to dictate terms to the studio, while DC is ultimately just “the hired help” at Warner Brothers.)
So the first thought ultimately leads to the second: There’s gonna be a lot of rebooting going on. Two of your three core members (Batman, Superman, Wonder Woman) need a new movie to establish themselves as part of the DC Movie Universe, and one of your second-tier members has a stinker that needs to be swept under the rug (a la Ang Lee’s Hulk.) How do you handle this?
You start by ignoring it. You’ve got an Aquaman movie, a Wonder Woman movie, a Green Arrow movie and a Flash movie to make. By the time you get through those four films, there’s a pretty good chance that you can go back and do a soft reboot of Green Lantern that isn’t so obviously an admission that the previous film tanked. Then, with five films under your belt, you can go in and do your Justice League film.
“Wait, what, five?” I hear you say? “What about Batman? What about Superman? What about the Martian Manhunter?” But honestly, I don’t think you need a movie to establish Batman and Superman before putting them in a JLA film. Batman and Superman are, at this point, such iconic characters with such iconic origins that babies practically come out of the womb knowing that Bruce Wayne’s parents were killed and he was inspired by a bat to fight evil. The last thing we need, pardon my mild frustration, is yet another goddamn retelling of the origin of Batman and Superman. (You can see how excited I am for the Man of Steel movie, aren’t you?) Just mention them from time to time in the other films, establish that they exist, and then throw them in the final flick.
As to the Martian Manhunter, he’d be filling the Nick Fury role on the DC end. He’d appear in all of the different movies, talking to the different heroes about how he’s getting them together to face a larger threat, one that he knows about as a telepathic space alien. (Maybe even one that killed off the Martian race…) This would link the various heroes together, whet interest for later films, and give audiences time to get used to the Martian Manhunter, who is definitely something of a legacy from a very different age of science fiction and comics.
So who would the villain be? Actually, surprisingly enough, I’d pick Libra. Go back to his original roots, where he was a supervillain attempting to steal the powers of the entire Justice League, and give a tip of the hat to his recent role in ‘Final Crisis’ by a) having him do so in order to better prepare Earth for the coming of Darkseid, and b) having him recruit a passel of henchmen to help him out. Then, in the Justice League movie, you pull a big surprise at the end…in the third act, after he steals the powers of Superman and the Flash and Green Lantern and seems pretty much unstoppable, you find out that the Martian Manhunter’s been recruiting a lot more than just the heroes who have movies. The final battle would have cameos by dozens of superheroes, from Zatanna to Black Canary to the Elongated Man to Steel to everyone who you haven’t gotten the rights to, all dogpiling on Libra and his Secret Society. In the end, Libra overloads himself absorbing everyone’s powers and blows up (a la his original appearance…) but the greater threat is still out there.
But all that, of course, assumes that Warner Brothers is interested in replicating Marvel’s success, something which has never been particularly clear from their actions. Certainly, it’s hard to believe that the people who made ‘Batman and Robin’ are interested either in making money or in bringing joy to the lives of others.

