I liked The Dark Knight over Watchman, because the Dark Knight required more creativity than Watchmen did. I mean, I love both movies, but Watchmen was basically a frame for frame rendition of the comic (for the most part), whereas the Dark Knight was a modern reinvention which set a new bar for the genre.
I don't know how anybody can't appreciate Ledger's joker. My appreciation for it has nothing to do with his death, but for my take on superhero films. What makes or breaks superhero films are the villains. There's a fine line between being over the top and unbelievable and being over the top while still maintining the audiences suspension of disbelief. I think Ledger (with help from Nolan) stayed on the correct side of that line.
Nicholson's joker was fine for the 80. But let's face it - that was a Tim Burton movie. F*** Tim Burton.