It always struck me as odd that RDJ was such an action star. He had a knack for choosing offbeat, quirky roles before he was Iron Man. He definitely worked outside of the studio system. That made his casting as Iron Man so out of the box because it seemed out of the ordinary, that he would be a part of a blockbuster, but obviously his skills and personality fit Tony Stark like a glove. (Bad pun.)

But he's been getting cabin fever it seems in regards to the Marvel movies and he's almost 60, right? So it is time for him to move on.

Pratt and Evans are still in the age range that they seem like they're able to carry the franchises for a while, but they're also motivated to be part of the series, maybe because they've always been studio guys and don't have the itch to be an capital-A actor.

I think Evans plays Captain America well (I've never read comics so I have no idea if Evans is bringing a sense of humor that isn't in the comic.) and I like Pratt enough. They don't have RDJ's charisma or star power (at least not yet) but the Marvel movies are the attraction in their own right and lacking a star seems like it would make the story able to cater to a wider set of characters.