I'll admit when people compare new coming DBZ games to Budokai 3, it really isn't saying as much as they usually imply.
But Budokai 3 represented a Dragonball Z fighting game that blew away it's predecessors. Ample amount of characters/transformations, long story mode, new fighting system, new moves and better looking graphics.
It's the gameplay that gets me. The gameplay was much faster/fun than budokai 1 and 2. You could actually dodge/teleport from individual hits/attacks, so you had to be on your toes when fighting. It actually felt like DBZ when you played against a good player/computer.