Ledger played the perfect Joker. Overall, I always felt he was an overrated actor; everyone said he was the next Hollywood superstar in the making, but I didn't see it. Look at Brokeback Mountain for example - his performance was wicked atrocious. But what he did in Dark Knight was wonderfully amazing. You really can't even tell Joker is Ledger. You remove Ledger from Dark Knight, and you have a mediocre movie, at best.
Oh, going back to Brokeback Mountain - one of the two gay dudes would have been the purrrrrfict role for starface. Truly could have been a bona fide [boner] masterpiece [mastu