Christopher Reeves was my favorite Clark Kent. IMO, the only actor ever to attempt to sell the "Clark Kent" disguise, which made him the only one where I could at least suspend disbelief to accept that those closest to him didn't know he was Superman. You could argue that Brandon Routh also played the disguised Clark Kent role, but I would argue he was trying to be Christopher Reeves more than he was trying to be Clark/Superman. Henry Cavil is probably my favorite Superman (Christopher Reeves comes in a close 2nd).
Val Kilmer was my favorite Bruce Wayne. In my head he fit closest to what I imagined Bruce Wayne to be like. Christian Bale is probably my favorite Batman.
Honorable Mention: Robert Pattinson is my favorite Nightwing. (Seriously folks, great actor, but he's not Batman)