To each his own. I think Jack's Joker sucked. The Joker is a tall lanky guy. Jack was short and fat. The Joker is sinister, yet humorous. Jack just kept trying to his devilish eyebrow arch.
Who, IMHO, would've made a better joker?
Jeff Goldblum.
But that's just me.
True, Nicholson surely didn't have the body for his role (arguably neither did Keaton), but as far as playing an insane homocidal maniac, I think he pulled it off nicely (mmm, I'm having Shining flasbacks). As for Schumacher, ugh, I just pretend his Batman movies don't exist.