Actually, how about Batman? It's true there were two cinema serials, but they were so cheap and obscure that they might as well never have existed. I haven't seen either of them, but judging by stills, they were embarrassingly dire poverty-row productions with a cast of nobodies in terrible costumes, and in one of them Batman was fighting some sort of not terribly PC "yellow peril" villain who wasn't in the comics.
But suppose the original grim, gritty Dark Knight of the actual Year One had continued to be a ruthless (and presumably Robin-less) vigilante who had no problems with a spot of casual manslaughter if he thought the baddies deserved it? How would a forties or fifties Batman serial or movie blessed with a decent budget and cast because adults were likely to be interested in it as well as kiddies have panned out?
The obvious choice for Batman would have been Burt Lancaster. Look at that jawline, and also, unlike anyone who has ever played the Caped Crusader, he was a genuine circus acrobat. And so was Kirk Douglas - wouldn't he have been a fantastic Joker? And how about Charlton Heston as Harvey Dent? And Tony Curtis as the Riddler? Of course, the Penguin was clearly based on Edward G. Robinson, and if they needed any of the more obscure villains, the first Clayface was blatantly Boris Karloff with a very slightly different name. I'm not sure about Catwoman though - probably Myrna Loy, since she ended up being cast as Fu Manchu's daughter. Which would have made her a shoo-in for Talia al-Ghul, except that she hadn't been invented yet.
Anyway, it's a thought, isn't it?