Hmm... just came to me, so how's 'bout we do a little summary of the main characters of all the FF games?
1 - None. Not even any actual characters in the party, really.
2 - None (or you could argue shared equally between the three)
3 - None. Like one, barely any characterization here, either, though there's a miniscule amount more.
4 - Cecil
5 - Butz barely edges out Lenna and Faris
6 - No one definite, but Terra and Celes are the only ones you could make any decent argument for. The best answer is simply that there's none.
7 - Cloud
8 - Squall
9 - The instinctive answer most people come up with here is Zidane, but you could also make a good argument for Vivi.
10 - Tidus
11 - Whichever one you create :P (stupid MMORPG breaking the numerical series)
And, just for completion, the spin-offs (at least the ones I can think of just sitting here):
FF Mystic Quest - Your renamable main character. Hardly an issue.
FF Tactics - Ramza
FF Tactics Advance - Marche
FF Crystal Chronicles - Whichever one you make (ala FF 11)
Bahamut Lagoon (it feels more like an FF spin-off than an independant title) - Byuu
FF X-2 - Yuna
Notice something here? We have only one female main character in all of FF, and that's in a spin-off. Or two if you count Terra/Celes. Makes you think about the latent sexism in the video game industry, or maybe just those who play it.
But then the question comes up, would more women play these games if they were more favorable to women in the first place?