Joaquin Phoenix is the perfect choice for Luthor. He just gives off a smart ass, evil vibe thats perfect. Cranston just doesn't give off the evil vibe enough, even though he was amazing in Breaking Bad.
I think Luthor has to be in the same age range as the Batman character, and at least slightly older than Superman.
So Phoenix is perfect. We have to have the corporate Lex, the genius who runs the media, and owns everything, and the one who eventually runs for president. The guy everyone trusts because he saved Metropolis and rebuilt it.
The Hackman/Spacey type Lex shouldn't be on screen ever again, its time for the more recent comic version to be put on the screen.
I hope Snyder picks someone like Phoenix, he will really knock it out of the park.
Another actor who I think would own the role is Billy Zane. Yes, he's been in many B movies and is not the big actor as he was before, but give him the right material and he will deliver. He was actually born to play Luthor, he can play smart, sneaky and just downright sleazeball with the charm thrown in. Goodness knows how many movies i've seen where i've seen him play parts of a Luthor type character perfectly.
I seriously think he would own that role, but because of people only wanting "big" stars, its unlikely he would be considered barring a miracle. People might consider him a joke or C list or whatever, but noone can deny the man can act. He would knock Lex Luthor out of the park, and probably give a rendition never seen on screen. Michael Rosenbaum is the closest we've seen to a modern Lex Luthor on screen so far, followed by John Shea.