Too may characters within too little time? Stories like the Avengers, X-men, Justice League, Green Lantern Corp.
I guess when I say too many characters, that's not really what I mean. I'm talking about properly developing such a large cast of characters within two hours, or the mistake of spending slightly more of their time on the wrong people. Im sure that writers and directors already know this, but are sort of hand-tied by the nature of the comic books and the stories they set out to tell.
Off the top of my head I can think of comic book movies that both failed and succeeded with the problem of pacing and character development.
How much is too much?