I don't really understand why out of all the Marvel movies, this is the one that gets all the attention. I mean, I know it's a crossover, but I get the feeling that if a Justice League movie showed up, it would bomb. The public seems very much on the Marvel side of the debate.
Marvel hit a good streak with the last bunch of movies... at least the movies based off 3 of the Avengers. Iron Man was a surprise hit, Thor did well, and Captain America was a solid action film. It's a team up, sure... but the first actual movie based on a super hero team up group. Sure, we had super hero team based movies... X-Men and Fantastic Four... but those were always teams. Not cross over team ups. And even in that case, due to certain movie studios having ties to certain other parts of Marvel's characters in long term deals hammered out
way before Disney bought them out, certain characters can't appear in movies.
With DC, there are two things. Herald's right. Marvel DID finally get its act together with their movies. DC, however, has yet to have a Non-Batman hit. They can't get Superman rebooted properly, Green Lantern was a massively expensive boondoggle that scripted way too much time for Hal Jordan to act like a schmuck when he discovered his powers and NOT enough Killawogg, and who the heck were they kidding with Jonah Hex? Like 5 people have heard of him. Not to mention the fact they can't even find a project for Wonder Woman.
Secondly... here's the stupidest thing you'll ever hear in the world. Warner Brothers owns all the characters. Warner Brothers makes all the movies and TV shows. You'd think they'd have free range of characters, right? They license EVERY single character separately TO THEMSELVES! That's why you can't see certain Batman villains in certain Batman productions. It goes all the way back to Riddler appearing in Challenge of the Super Friends, but not in The New Adventures of Batman... while the Joker and Penguin aren't in the other show for the same reason. That was when it was licensed out to different companies, sure... but there's some really complicated stupid thing that goes into details I don't know about.
So a JLA movie might not even be possible for that reason.