Most of the criticisms of the Joker are valid to a point; they just tend to be little more than superficial, however. 
 
There are details that Nolan didn't include, like the Joker venom, but the core of the character is there like it's never been before. The psychological profile of Nolan's Joker is the summation of every great version of the character. His take on the world, his relationship with Batman - it was the epitome of who the Joker is. 
 
As much as I love him, I didn't get that from Nicholson's Joker. He got all those superficial details right, but he always felt like little more than a criminal with a gimmick. It always seemed like he saw Batman as little more than an obstacle to get past, rather than an eternal rival/bizarre "soul mate."
 
Even TAS, which is for the most part definitive Batman, didn't take (probably due to the restrictions of a 23 minute a week children's show) full advantage of the Joker's profile. He was near-flawless, but limited to that "scheme of the week" format. TDK was able to flesh him out a lot better.