Norton and RDJ partnership would have been epic. Would completely overshadow Hemsworth and Evans. Norton brings intensity and prepardness to every role and RDJ is probably one of the best actors of our time, glad he didn't go the Sheen route.
Iron Man I and Hulk 2 (??) are still my favourites though.
I'm sure "character actors playing superheroes" has been discussed enough on this board but I'm still very much in favour of it.