No Pitt, Clooney or Damon. All are too well-known and won't dissolve into the character, though Pitt is a talented actor. None would do it at this point in their careers.
No to Dominic West. I love
Punisher: War Zone, so for me he already played a great (over-the-top) supervillain as Jigsaw.
Heyerdahl looks like he would make a good Brainiac, because he's strange and alien-looking with a weird-shaped head. Not as Lex though.
No to Craig. Again, too well-known, already has an iconic character as Bond, and I just don't see him as Lex.
Patrick Stewart - no way. Too old and too obvious (the only reason anyone is thinking of him at all is because he's famously bald).
I do like the idea of Clive Owen: has the right look, as does Jason Isaacs. Daniel Day-Lewis would be amazing, but I don't think he'd do it.
Just going to throw a few wild cards out here...
What would people think of
Mark Wahlberg? Wahlberg may not be the world's most talented thespian, but he does play a convincing badass. I don't know if he could pull off the part of a brilliant scientist, but I have no doubts he could bring the cold corporate businessman Lex to life, and he can certainly appear ruthless and highly competent.
Armie Hammer? Seems like a young Billy Zane, but taller and arguably a better actor.
Two options I would be much more enthusiastic about...
Josh Brolin. He's proven himself a talented actor who's adept at disappearing into a role.
Sean Penn. 'Nuff said.