obviously based on the comic book.
i think this would be a great movie, watching our favorite superheroes battle it out.
if they include all the characters, even if they dont have there own movie, include the x-men universe and the avengers universe they have already established, along with lone movie characters like spider-man. if they wait until after their "phase 3" for the avengers i think they would have enough heroes to succesfully do this, if they feel they should only use characters that have their own movie.
let me know your thoughts and how they could go about this