A title perfect for gamers of any age. It's safe for kids as there's only animated violence and it sports a simplified control scheme, yet it has enough content and challenge to keep experienced adult gamers entertained for quite some time.
There's enough content and replay value to keep you busy for hours -- even more if you hook up with friend. Factoring all the elements this title offers makes it a no-brainer for anyone who's wanted a fighter that's simple to play, entertaining, and offers long-term value.
It is limited in a few ways, namely in the number of characters (a total of 16 with unlocks) and the depth of the fighting system, but it is also something I can see as a great party game for groups of casual gamers of any age.
Grand Battle might be alright for two-player games, but the single-player experience is worn out in six hours or so, and I'm not sure how many people would want to jump into a tournament with this fighting system.
Light on substance and heavy on style. If you're a One Piece madman who simply has to have everything to do with the series, it's not a horrible game. It's just not exceptional. As a multiplayer party game, it's good for a quick fix every once in a while.