I may always be Heath Ledger fan but now I'm literally all in on Cameron Monaghan's Joker. It not only stayed loyal to the comics but it was a absolute breath of air. Plus, he not only played one Joker-ish character but two. What Joker has pulled that feat off before? And he is also the youngest to ever play the role. A great accomplishment indeed. Monaghan's Joker's final form post chemical bath was hella terrifying that it gave me nightmares and inspired a lot fan art from different artists and animators. In my book, Cameron Monaghan's Joker will either 2nd or 3rd on my list of best Jokers.
And to Joaquin Phoenix's Joker
I know its a little premature but..
Welcome to the Family(of Jokers I mean)