Oh, Mark Hamill...what he did for the Joker was breathtaking. Bruce Timm and everyone who worked on and in Batman: The Animated Series were legendary...
But Heath Ledger was a damn good Joker--a very new take on a very old character. I thought his voice was pretty decent, very...strange, and I love to imitate it. I mean, compared to Bale's Batman voice and Eckhart's lack of a Two-Face voice, Ledger did quite well.