First of all I must stay I am a Naruto addicted so my recommendation may be biased xD
This will be a long analyses, but I am hoping useful for people interested in the game.
Naruto is a 3D fighting game developed thinking mostly of the fans of the anime. A proof of this the extent of the cutscenes in the story mode (some of them go as long as half an hour - you are basically watching a tv show), which means that if you are not a fan you will probably not enjoy this game very much. It is also advisable to have a gamepad
to play, since fighting style games are not really developed for keyboard and this one is no exception.
You have 3 game modes available: Ultimate Adventure, Free battle and Online.
Starting by the Ultimate Adventure, the story picks up after Pain destroyed Konohagakure and goes until the end of the Fourth ninja war (giving it an alternative ending to the manga). The main story takes about 10-12 hours to complete, of which probably 6-8 are cutscenes. After you finish the main story there is a load of side missions to do, and if you want to complete everything to 100% (S-rank every fight with bonus) it can take close to 30 hours. The art is fantastic, with little to no bugs in the free world map, and with very interesting side quests in my opinion. In here was where I learned the game mechanics which are pretty simple but still manage to make the game enjoyable.
After you finish the Ultimate Adventure more than 100 characters will be at your disposable to use in Free Battles. In this section you can also do the 100 misssion battles with different challenges each, which should take you 10 more hours if you go for the 100% again.
Lastly the Online. It is terrible in my short experience. Games crash a lot (I wasn't able to finish a single combat in 5 tries and have a 100mb connection), and there is also a significant delay between when you press a button and the action takes place. This could be a turn off for you if you are buying the game for the online, but for fans like me, the offline mode will keep you very happy.
I saved the best for last: YOU CAN USE MODS IN THIS GAME!! It is awesome, you can add characters like Goku Naruto, change characters movesets and even add new stages, all developed by a fantastic community and just ready for you to download xD
+Simple but addictive gameplay
+Lenght (40 hours offline only)
+Ammount of characters
Hope I have been helpful (: