Some of the top reasons why Jack Nicholson's Joker is totally better character compared to Heath Ledger's bizarre and un-Joker-like creation:
1. Nicholson's Joker was actually very funny.
Heath's Joker had no sense of humor at all :D
2. Nicholson's Joker was incomparably closer to the authentic comic book character.
Ledger's Joker was a completely new character, unrelated to the original in almost every aspect of his interpretation ;)
3. Jack's Joker had much better lines.
Heath was usually mumbling some maniacal and depressive Emo crap, totally out of the character :P
4. Jack's Joker killed more people in the original movie
So much for the Ledger's alleged "darker and scarier Joker" :)
5. Jack Nicholson's Joker had a very interesting On-Screen Origin, and a motive for revenge (so did Batman)
Heath Ledger's Joker had nothing 😁
6. Genuine Joker was an euphoric type of lunatic, closer to Schizophrenic, rather than Ledger's anarchistic Psycho type
Jack wins again 😜
7. Finally, Jack Nicholson's Joker was classier, more stylish, he had better makeup, more convincing smile, and he was an expert at chemistry, his weapons were absolutely cooler compared to Ledger's Joker 👍
Conclusion: The only reason why people are glorifying Ledger, is because of his untimely and infamous death, but when it comes to real acting quality, he is not a match for Jack Nicholson.
Modern kids are obviously not familiar with the original Joker character, or are infatuated with Heath's so called "darker version of Joker" - Just to be clear, there is only one original story, while the "other versions" are just unnecessary modifications, usually ranging far away from the indigenous story.