The series has changed, with disastrous results.
First, more complex button input sequences have been added to all of the Ultimate moves, making them far more difficult to pull off. This time around, Ultimate moves can't even be used without entering "Hyper Mode," in which your ki (energy required for special moves) cannot be manually recovered, and decreases constantly until it is empty, at which point Hyper Mode will be canceled. Unfortunately, that means that if you are in Hyper Mode and your ki has become too low to initiate your ultimate move, you're out of luck. What's more, even if you do have enough ki, if the initial strike misses the opponent, your ki meter will drain completely, canceling Hyper Mode anyway. The upshot is that you've got one chance to pull off the move, and it's not easy to do it again. These elements serve only to muddle the simplicity of the tried and true formula used by the previous games.
Second, the special moves a character can use have been greatly reduced in number. In the first two games, every character shared a set of "Physical" specials in addition to several "Ability" specials that were unique to each individual character. In this game, the Physical specials have been removed completely, greatly limiting your choice as to how you fight. They have been replaced with "Item" moves, which are by no means essential to victory.
Although the core gameplay has deteriorated, the story mode retains some level of entertainment. Each character has a unique story, and it is carried out with some RPG elements. The RPG elements are a great addition, but you can only save data from one character's story at a time, and the stories are all tediously long. Bottom line, the more or less increased quality of the story mode doesn't make up for the decreased quality of the gameplay.
The graphics and sound have the same beauty as those in the prior installments, but why settle for this game's good graphics, good sound, and bad gameplay when you could have the other games' good graphics, good sound, and GOOD gameplay?
Some departures from tradition are met with success, while others are met with failure. If you're a fan of the Budokai Tenkaichi series, you won't be disappointed by this game, which is essentially the middle step between the Budokai and the Budokai Tenkaichi games. But if you prefer the style of the previous two games, as I do, you'll be very disappointed at the changes made. If you haven't played a DBZ fighting game before and are interested in this game, do yourself a favor and play its predecessors instead.