I dont think Ledgers performance was overrated at all. Infact as a result of the hype i think alot of people just want to think that. Now im not saying Shavsre is one of them because its your opinion and i respect that but i think theres alot of people who just say it for the sake of being controversial. While i agree somewhat with people who say Begins was better i think Begins is massively underrated compared to The Dark Knight.
Personally i think weve been lucky with the 3 main incarnations of the Joker onscreen. Nicholsons was perfect for Burtons Batman as was Ledger for Nolans. For me though Hamills joker takes the biscuit. He was excellent, and when i imagine the joker, his voice is the one to come into my head.