Fun for all, but being a naruto fan helps
The gameplay is good, with 4 difficulty settings (after you've unlocked level 4) and other ways to customize gameplay, such as match length and attack power. The only thing they missed in that department was controlling how fast chakra regenerates. I'd like it to go a bit slower. The graphics are a good style for an anime-based video game, but they could use some refining; the pixelated shadows are a huge graphical letdown.
A few missing characters, such as Kiba and Choji, leave something to be desired, though this is being corrected in the sequel. Nevertheless, 20 characters leaves a lot of options.
The Mission mode: Essentially screnario fights, mostly taken from the anime. Fun, with 3 difficulty levels, but it could stand some improvement. No cutscenes, just text and images. This isn't necessarily bad: Fire Emblem fans like myself will feel right at home.
Single player: 10 1-on-1 battles. Each battles is best 2 of 3 rounds. Each round is 60 seconds. Opponents and stages are random. Fun if you've grown addicted to a certain character, or if you need to practice with someone for mission or multiplayer modes.
Multiplayer: Your basic fighting game. As previously stated, you have a lot of control about things like # of rounds and attack power. Very fun. Wii-mote is used for weak attacks.
Vs. Mode: The same as multiplayer, but against a computer. Still a great way to have some fun, but you're limited to 1-on-1 matches. It would be nice to have a 4 player free for all mode, like the multiplayer has.
If you like Naruto, definitly check it out. And if you like the game, consider that I found it new for $20. Even if you don't have friends to play with, Vs. Mode and Mission mode may be worth the money alone, so I recommend trying it once to everyone.