This is every ultimate ninja fan's dream come true!
First, after completing most of the side quests in the story mode, Guy will be standing near the tree stumps at the training area, and if you talk to him, he will offer you the ability to partake in a survival mode for the 2D aspect of the game. So, for the first time ever in a ultimate ninja game, there's a survival mode to the fighting.
Second, the closing of the save Gaara arc is complete. That means final form Sasori is here along with puppet form Chiyo, and my personal favorite, Sai. The battles between certain characters are unforgettable. The battles of Sai versus Deidara, and four tailed Naruto versus Orochimaru, were simply epic!
Third, the story mode has been muched improved over the last game. It's not as difficult, especially since there is much less platforming, but the game now offers team travelling and battling across the three dimensional naruto world.
Fourth and last of all, the gameplay has been changed considerably. It's not just the introduction of the new support character system, which forces players to rethink their time tested fighting strategies, it's the fact that it's easier to pull off long stringing combos, like we all could do in the second game of the ultimate ninja series. Though now, it is also a lot easier to recover from a long strung combo, so everthing balances itself out.
In the end, this game, is the pinnacle, of all the ultimate ninja games. It's not just the best in the series, it also stands apart from the rest due to the new gameplay additions to the 2D fighting. It is more like a whole new take on the ultimate ninja series, and less like its final installment on the ps2.