Over the years I have seen lot Lexs come and go on TV and Movies and many re makes of him in the comics books Video games. So far what I have learn is That Hollywood has not set the bar very high to have a good Lex Luthor in a movies. Hell The Tv show Smallville did a better job in my opinion.
My first thought who could play him was Michael C. Hall from Dexter. Also keep in mind that Lex doses have be bald to play this part.
My second player for this role is Dwayne Johnson
third guy is Billy Zane