Naruto Ultimate Ninja FINAL endings?

I realize this question is old, but maybe someone will still care for an answer.

I assume you are talking about PS3 version. If so you don't get extra endings. You get story/ cut-scenes when you get the secret factor challenges (don't know the official name) and just beat battles. Rank doesn't change the amount of story you get.

You do get a trophy for beating all missions on S-rank, but apart from that nothing. In last Naruto game I bought and got everything and was pretty disappointed, because buying all the cards and titles took a while and they didn't even carry over to the next game.

IF however you are talking about PS2 version, then there's absolutely nothing to be unlocked by the S ranks.