I think it would be a bad career move for him to do 50 Shades. One of my friends convinced me to read the first book, and I walked away really disturbed by Christian Grey's character. I've read other series with S&M before (Ann Rice, the Kushiel series), and I have enjoyed them, but I have never disliked a protagonist as much as this one.
He is controlling, condescending, insecure, twisted, mentally whacked, cruel and he can only get off by physically hurting the woman he loves. I really don't care if he changes in the next couple of books; he's horrible in the first one and that is who the person playing him in the first movie will need to embody.
Christian Grey is literally the opposite of Clark Kent and Superman in every way, in my opinion. I actually do believe that Henry has somewhat of a responsibility as a role model during the years that he is playing Superman. He doesn't have to play characters who are morally perfect, but I believe that 50 Shades sends some really whacked messages about relationships to young, impressionable women, and I hope he chooses to take the high road and refuse it.