I don't get the Cranston thing. Just because a guy can act and is willing to shave his head, it does not necessarily follow that he would be a good Lex Luthor.
If that's the only qualifier, how about Patrick Stewart?
Cranston is capable of doing vicious and intelligent very well and that would be perfect for Luthor. He's also the perfect age for the character. Patrick Stewart is too Shakespearean for the part. The problem we have with Eisenberg is that we're afraid he's going to portray a young, hip, cruel, and geeky Lex rather than an older, reserved, and brutal Luthor.
Ask yourself who would be better for a live action version of that scene. Bryan Cranston or Jesse Eisenberg?