Now that I think it's not "too soon" anymore, I'm going to bring this up.

Heath was a mediocre Joker in The Dark Knight. He didn't seem unpredictable like all the other jokers. Whether in the cartoons, comics, past movies, etc, the Joker was always unpredictably insane, laughed at everything, and made cheesy jokes.

All Heath did was lick his lips when at all possible. The backstory wasn't even that great. "Do you know where I got these scars?" When I heard the first story he had for them in the movie I was intruiged, but after the second and third time I was completely done with him.

I liked where the story took Joker. A man that could turn the people against their own faith. But Heath didn't do it for me...

YouTube - Mark Hamill's Infamous Joker laugh

^ Mark Hamill, voice of Joker in the animated series AND Arkham Asylum for PC, Xbox360, and PS3.

Jack Nicholson is still the best, however, this is my pick for the person who would have played the best joker in The Dark Knight.