Yuna wasn't the main character of FFX...no matter what you say. The best references come from the game itself, and with Tidus almost always being thenumber 1 character being controled, and of course the famous "This is my story" quote, it's hands down obvious who the main character is.

In FFXII though, I see no one as a main as well like FFVI is. Sure Vaan is the guy who you see if you have more than one character in your party and you're walking around a town, but it's pretty balanced in FFXII. I like a mix of both every once in a while.