A few points about B89's Joker:
GOOD
1) Easily the most recognized comic-book villain on the silver screen (bigger than Hackman's Luthor, McKellan's Magneto or Dafoe's Goblin), all due to Nicholson's on-screen performance. Ask any random (i.e. non-internet fan) on the street about a comic-book villain, and B89's Joker will always be mentioned.
2) Probably the most quoted comic-book character on screen. e.g. "Where does he get those wonderful toys?", "Have you ever danced in the pale moonlight?" and "He stole my balloons!"
BAD
1) It was never the Joker (as played by Jack Nicholson), but the reverse. Just as in B&R's Mr. Freeze, the star was bigger than the character being played, making it impossible to appreciate the full extent of the Joker's personality.
2) The conversion of Jack Napier to Joker consists of the skin bleach and perma-smile only. In terms of personality, Nicholson portrayed the two characters as essentially the same (making his 'transformation' redundant, and adding zero character development).
3) The chaotic nature of the Joker was far too 'ordered' (if you'll pardon the pun). He takes control of the mob in Gotham, hooks up with his boss's girlfriend, and uses the resources to CONTROL the city. Granted, he kills people randomly (without remorse) and creates scenes of chaos, but the character appears more interested in Vicky Vale (WHY???), or
4) His relationship with Batman. Firstly, the Joker killing Bruce's parents adds another twist to the relationship, but screws up everything else. As a character of chaos, the Joker is both fascinated and disgusted by Batman (forever stuck between wanting to kill him, and wanting to keep him alive), whereas in the film the Joker just wants him dead.