Re: Avengers Assembled: News and Speculation - - - Part 69
Whedon is a creator, avengers probably doesn't have as big a place in his heart as his original work due to the fact that it was something he signed on to and not created himself. He likely considers some of his original creations great but not the thing he was just singed up for.
It's sort of a reason you won't see very established directors jump onto other properties, they like to create the worlds themselves.
I think the only reason Disney got him back is they must have offered him the moon when it came to his salary bump up.