You know, of all the cinematic versions of Batman I don't think there was one actor who didn't bring anything interesting to the role.
Adam West is mostly remembered as a joke but for as silly as his Batman was, his Bruce Wayne was actually very good. I always thought he could have done a fine job playing a more serious version of the role. There was kind of a class and dignity to his performance
Keaton was portrayed him more vulnerable and unhinged, quite fitting with early Tim Burtons gothic horror sensiblities. And he made Batman and Bruce really feel like two seperate entities.
Val Kilmer is probably the most underrated one. He had the perfect look and I think he was a great choice for a more lighthearted Batman. Not as tortured as Keaton though still with his damons, can do a swashbuckling hero and a more grim, stoic caped crusader.
Clooney was a great choice for Bruce Wayne but a pretty bad choice for Batman, though I wonder what he could have done with a better script. Just like the movie went back to the sensibilities of the Adam West era, so did his performance.
Bale did a fine job turning Batman into a believable character. It's easy to make fun of the voice but he had a strong presence. In a lot of ways his interpretation was an evolution of Keatons, one that didn't entirely capture what made Keatons so great but brought enough to the character to make him interesting. For all the faults of the Dark Knight movies, Batman himself was allowed to have an arc in them, which is pretty novel for them.
Affleck did fantastic work turning Batman into an antihero , even a villain in BvS. He did a pretty good job giving us a grim, hateful, violent Batman that still seems human. BvS approached Batman as a broken man with deeply internalized trauma who uses violence as an escape and Affleck was believably bitter, deterministic and grim.
So, who's gonna be next? Depends on where they're gonna take the character. Jake Gyllenhaal could pick up where Bale left of and probably do a good job in a movie more focused on Batman as a character rather than the things he reacts to. John Hamm... eh, not crazy about him. Probably fine for a more lighthearted, humourous take. Idris Elba... well, I'd be ready to bet on the dark horse (no pun intended) but will the world accept a black Batman? Worth a try, I think he'd do a fine job as an actor.
If they do Batman Beyond though... well, I know we're all thinking Eastwood, here me out though: How about giving Clooney another chance? He may not have been much of an active Batman but aging Bruce Wayne? I think he could nail it.