IMO, the original was slightly better -- they spent a lot more time on glitzy graphics this time around, which is probably good for sales but I just found them a distraction. And they made a conscious decision to broaden the musical selection, which again should broaden the appeal, but personally I found the electronica-heavy original better.
Still, the sequel is better than anything else I've played in ages. And the sequel gets the difficulty levels right this time, so that a wimp like me can get a lot further in the game. Ah, relaxation through a good beat...