Nothing against Ledger, but he gets too much credit for his Joker role. He deserves it, but watch the movie again, its pure perfection. Bruce Wayne/Batman, Harvey Dent, Commissioner Gordon, Joker(Yup, I'll take Ledger's performance over Nicholson's anyday), Every one of them nailed their own performances, sadly overshadowed by Ledger. All the actors gave their A game. Other than the obviously terrific script, and direction.
About the comparisons to the original, yeah I do get that their inevitable, but you simply lose the credibility if you make your judgments that way, particularly when the film makers kept telling that its a pure re-imagination, based only on the comics, not on any films from the past.