Cary Grant sounds like a good 1940's Superman - or even Fred MacMurray (I forget the film, but he appears in full superhero getup as part of the leading lady's dream sequence). In in the '50's, Rock Hudson would've been (at least physically) perfect.

Back to Batman (at least peripherally): As mentioned on the commentary track for SOME LIKE IT HOT, Jack Lemmon is very Joker-like: heavy makeup, wide grin, manic demeanor, etc. Combine that with his OTT moustache-twirling villainy as Professor Fate ... well, whomever played Batman would've been blown off the screen.

But I digress ...