Mark Ruffalo is too goofy looking not nerdy this movie gonna be a bomb if they pick him.
What's so goofy looking about him? He's also a good actor and can play intense parts, as we've seen in Zodiac. Ed Norton was pretty good, and I think they should have tried harder to keep him, but if he really is as difficult as they say, I can't blame them. It could cause some nightmarish situations on a huge project like the Avengers.
In any case, I doubt Banner/Hulk will be one of the lead characters in the film. He'll probably be tertiary to Iron Man/Captain America/Thor. So, bad casting for Banner is unlikely to sink the film.
What I AM curious about is who the villain/s will be. Skrulls? The Grim Reaper? Ultron? Kang?