When it comes to the two very talented actors who portrayed the joker, it can be really tough to decide who portrayed this iconic DC character the best.
Jack Nicholson stuck more to the origins of the joker in his 1989 batman movie. He was more goofy and quirky just like the joker is in the comics. As for anyone who has read the comics and seen the movie, he also uses the same moves Eg with his spray button that melts faces or the buzzer in his hand that electrocutes people. Unlike the dark knight film, here we see one of the origins of the joker as it was portrayed in the comic the killing joke. Jack napier as he is known in this film, turns from normal to mad after being pushed into acid by batman. So this is a bonus if anyone wanted to know the origins of the joker and hasn't read the comics (this is still debateable as Noone truly knows the true true origins).
Then we move on to the anarchist joker portrayed by Heath Ledger. As he was seen in The Dark Knight movie released in 2008, there was a lot of controversy amongst the joker lovers if heath would be able to pull it off (same way everyone is now with Jared Leto). Of course he came through and created the most memorable portrayal of the joker to date. The first thing that made him stand out was obviously his makeup. Unlike the comics, here he just paints his face and not for it to become like that after dropping in acid. The other thing was obviously the scars that made him stand out rather than a permanent smile. As for origins in this batman story Noone really got a backstory. Noone knew where he came from and no records of him were found in Gotham and to be fair this was well planned by the directors as they didn't give him any origins, he just showed up. In terms of weapons, he was more knives and guns everything simple and not of the DC origins.
With all thay being said when you compare the two actors, Jack Nicholson was still a bit put of his comfort for the role but Heath Ledger turned into a completely different person for that role. It is rumored that he stayed isolated from everyone just to prepare himself for the role as well as keeping a diary of his thoughts (which his father showed a couple of pages and you'd truly think heath went mad). As for the winner my personAl pick would be Heath Ledger. He gave a new twist to the traditional comic joker in terms of looks and personality and made himself the most memorable. RIP Heath Ledger
Now this was just my pick. Obviously there's more to it and would like to see who everyone else would pick as their favourite.