Chrono cross a FANTASTIC game. Just look at the reviews it got. It is a great game, it just doesn't pull its weight as a full "sequel". You have to look at it like a completely different story in the same universe. Chrono cross had excellent music, but the combat is pretty unique and fun especially for its time, and the story has many different paths offering great replay-ability and so many things to discover. The only issue I truly agree on with critics is the fact that too many playable characters without any real story exist.
It wasn't quite the "Chrono Trigger" sequel most people expected, but it's a magnificent game by its own right.