4. Jon Hamm
Jon Hamm previously played Lex Luthor in a 'Funny or Die' segment, and he is one of the actors on the shortlist to be the new Batman. Whilst I do think he would make a great Bruce Wayne, he could make an even better Lex. His character Don Draper on AMC's Mad Men makes me believe he could play a good antagonist, despite being the protagonist in that show. It's always good to have range isn't it?
He may voice a villain next year in the Minions movie, but to have him physically play a villain would be even better. Judging by his appearance on Mad Men and his Golden Globe winning acting abilites, this man could pull off the businessman side of Lex quite well whilst playing the celebrity everybody loves.