Interesting...I just watched it again for the first time in about 15 years and I thought the exact opposite...I don't think it has held up very well...I'll take Batman Returns any day over Batman...
To be honest I've seen both of Burton's "Batman" flicks so many times now that I'm kinda burnt out on them, but I happened to be watching this one with my sons, who were seeing it for the first time ever (my 11 year old got the DVD for Christmas) and they both LOVED it. They were laughing at all of the Joker's stupid stunts, cheering whenever Batman punched out a goon, going "WHOAAA!" when he crashed thru a skylight or swooped off a rooftop, etc... so I enjoyed watching it through 'their' eyes way more than I probably would've if I were watching it yet again by myself.
I think that Keaton's acting was the worse part which is strange as I don.t remember it being that bad...he seemed very out of place...Nicholson was still very good...