Are Batman Begins and The Dark Knight better movies than Batman's first major big screen adventure? Yes, I think they are. But I think that doesn't mean we suddenly have to dismiss Burton's version of Batman. It was still cool and it introduced a world of us familiar with the campy 60s show what could really be done with the character. And without it, we wouldn't have Nolan's terrific versions of this fine hero.
And let us not forget Jack. I went in to that movie knowing Batman would be a cool dude, but was totally blown away by The Joker. It's hard for me to compare Jack's Joker with Ledger's, as to me they are two totally different characters. I tend to like both of them, but I loved the crazy energy that Jack exuded as the character. Whereas Ledger's Joker seemed like a psychotic who liked to wear makeup and cause anarchy, Nicholson's Joker truly came across as a deranged clown, which is how I tend to picture the character myself.
Once again, I understand that as movies, Nolan's movies are more mature with better characterizations, but let's not rewrite history and suddenly make Batman '89 a piece of crap. It might not be as good, but it's still pretty cool.