How many characters can you have.

 With the elements coming together for the Avengers movie and the long standing talk of a JLA movie, I wonder if there is a limit to how many lead characters can you have in one of these super team blockbusters and still have a fluid character driven movies. Marvel seems to have the right idea by setting up the characters and their orgins in solo movies then bringing them together, but I question whether these larger than life icons can share the big screen and not over whelm the movie as a whole because the sum of its parts is greater. For the Avengers, we know that we'll have Iron Man, Thor, Cap and Hulk. Should that be it? Can the the movie support any more heroes? I'm not the biggest Hank Pym fan, but he is a long standing part of the team and should probably be in the movie, but is their enuff screen time and what about Wasp? The main characters are one thing and let us not forget the all of supporting characters that are being introduced(Nick Fury ,Black Widow , WarMachine, Thunderbolt Ross, Betty, Pepper,etc) not that they have to be used, but we know Fury will be. So can they pull this off? How many characters do you think they can insert into a single movie before it stops being a film and becomes just a big budget, plotless parade of superheroes and special effects? How many members of JLA could make a great movie?