Yea, I think that Diablo II's music fits each act perfectly. I think Diablo I is a lot more evil sounding - so I hope they combine the concepts of both styles of music into Diablo III.
The people that go online for Diablo I are all hackers. It's so tainted. It was fun in the legit days however. I stick to Diablo I single player for the music, monsters, items, skills, and of course, Tristram.