So these heroes each had their own movies. Don't let that fool you into thinking the game has been changed. When Avengers comes around, these super heroes will be reduced to two word archetypes (loveable jock, paladin leader, sassy chick, snarky egotist etc.) and it won't make much difference to what will probably be a simplistic, generic, super-team-vs-evil-super-villain, plot. Like the one we've seen in 5 X men films. And two Fantastic 4 films. And even that The League of Extraordinary gentlemen film no one likes to remember.
It has been done.
It has been done.