I liked the sheer Number of bosses in this game, If you count any thing that uses the boss music, the giant bowser scenes, the final boss, the X bosses, and the optional bosses who have been mentioned in this topic on page 1, there are more then 20 bosses, more than the other 2 games.
Unlike most people, I actually liked the final boss music and from what I have heard, most of the music in the game was done by a musician who did some music for Kingdom Hearts. Which probably explains the final boss music.