Some of you might already know about this, but for the rest of you here’s the story: when Sonic CD was released in the US, about 2/3 of the soundtrack was altered for some reason. While the American soundtrack is very much above average, the Japanese soundtrack is one of the best OSTs ever released. Here is a brief sample of the awesomeness.
http://www.youtube.com/watch?v=8tXtzlUDTD4