Well... Michael Keaton could pull off Batman, but not Bruce Wayne. No way. I'm sorry... He is and always will be Mr. Mom to me anyway. And middle-aged, sorta on the verge of balding Bruce Wayne is totally not it.
Val Kilmer couldn't pull off either of them...
George Clooney... that movie is a farce, I'm sorry. But he's OK for the billionaire playboy image, though. Totally.
Christian Bale, to me, was absolutely magnificent as both. But that's just me. (I also totally dig the tumbler, but again, that's just me. it's so much more like the comics I've read!)
And whoever the guy is, playing Superman in the trailer above... He's flippin' yummy!