There are plenty of characters to unlock through playing story mode. Not as many as Busokai 3, as this game goes up to the Cell Saga only... and also has Broly and Bardock stories as well.
It's not the sheer number of characters that truly matter though, it's how different they are. How many characters in budokai 3 were nearly all exactly the same? Most of them were the same.
Burst Limit, each character has a different feel. I like it.
Haven't played a DBZ game since Budokai but after I saw the commercials and what the graphics look like I am certainly considering pulling out my old DBZ merchandise running to gamestop buying it then listening to three hours of Kamekameha!!!!