A couple of things:

A) Did you manage to beat the Joker on the NES version? I think this is one of the hardest games I've ever beaten in all honesty. There were a few parts where I was having to spam my projectiles and I was actually running out of them during the game, so getting the Joker was pretty difficult for me. That fight was pretty crazy if I remember right though.

B) What did you think of the music? This is one of the things I really like about Batman on the NES. I haven't played Batman on the Genesis, but I'm sure I'd probably like the music there too. I just generally like the soundtracks on those old Sunsoft games.