There not being power structures in Naruto...well, that's life. You can never be certain that someone will win over someone else.

I mean, you could go by rank, but that's hardly foolproof. I mean, Naruto is still a Gennin and he's could probably beat alot of Jounin. It's just not reliable. Because there's alot of reasons why someone might not be the rank they should be.

It's like's been said. There's a kind of "rock paper scissors" thing in the show too, where maybe someone can easily defeat taijutsu, but is terrible at beating genjutsu. That person could get beat by a seemingly weaker genjutsu user while defeating a much stronger taijutsu user. It's all about what techniques they have.