This is one of my favorite comic movies but I don't think marvel should sweat with DC's movie marks. All they got going for them is Bat Man and Superman so far.
Ledger makes a good Joker but only when it comes to Jokers planing and sadistic sides. No one is crazier than Nicholson. If I had to choose to be killed by Nicholson's Joker or Ledger's Joker, I'd choose Ledger because he would either kill me or have someone else do it. Nicholson's Joker would make me live a degrading month because he'll attack the deodorant, soap, and mouth care factories then poison the water supply with hallucinogenics and make me kill my sister because I thought she was the Easter bunny and she wanted to eat my brains (I can't make this stuff up). Then sprinkle money over my city to make me vote for him for mayor.
I also believe George Clooney had the potential to be the best Bruce Wayne. I blame directors and writers.