There are built-in codes in the game. I also used it, I can't be bothered to play 10 hours VS for every locked character. There is still a LOT of stuff to be unlocked from gathering points (character models, super move movies, artwork, music, effects...).
It's really fun though, especially if both players like Naruto. It's fast paced, has good animation, very tight gameplay. Throw escapes and interesting and lead to reversal to reversal to reversal until someone slips up.
It also seems quite balanced with the exception of Itachi, that guy just kills everyone else, and the weaker characters without supers (Shizune, for example). Itachi has a super that does moderate damage, but after it the opponent can't move for 5+ seconds. Another super has the opponent really slowed down. Oh, and on open levels without any side barriers, Tsunade can just happily smash everyone off the stage with her regular punches.
I'd say it's a solid 8/10, possibly 9/10 for fans. Easily as good as GNT2 and probably one of the best anime adaptations I've seen.