When it comes to Hamill and Ledger, I don't like to make a definitive statement. Both are top notch for entirely different reasons and are going for to entirely different visions.
Hamill's Joker is arguably better scripted. His lines are more solid and contain a lot less on-the-nose dialogue. And, as the original author of the post said, he balances charming and sadistic really well. Hamill's Joker is a real bipolar sociopath. I mean, DSM-V textbook case. It's a really well put together psychology.
But Hamill, as good as he was, doesn't hold a candle to the unbelievable depth complexity of Ledger's performance. All the quirks, like the twitches, the licking of the lips, the sudden shifts in tone and the absolute smugness hidden beneath the layers of performance; Hamill put up a good show, but Ledger's performance is not to be topped. On the other hand, Joker's script in The Dark Knight at times doesn't feel as natural. All dialogue in fiction is obviously contrived, but there are a couple of times where things the Dark Knight's Joker says feels contrived. But, jumping back onto the first hand, Ledger's performance is so incredible that unless you're closely analyzing it, you won't notice it.
So yeah, I'm giving a tie between Hamill and Ledger. None of the other Jokers even come close.