I love FF but didnt have posted here yet because I was still playing FFXIII when it was being discussed, sorry to bring it back
But I just finished XIII today (have yet loads of missions to finish) and finished XII last month so I may give a better opinion now.

Just for background info, I have finished all main FFs, except for FF2 and 5, which I begun playing but stopped for some reason. (taking FF11 and 14 off the list)

My all favourite FF is and probably will always be FFVIII, just because it was my first BIG rpg and I loved it so much, from the characters to the battle system, the summons, the spells, abilities, card games, the intro song, side quests and everything else.

But I have to say that despite all the hate for FFXIII, I think it became my second or third favourite now. The battle system is the one I had more fun with and the story is showed so well that its hard to not like the characters, smile and cry with them.

If I would classify the top 3 FF's in the 3 main things that makes a good RPG IMO, besides soundtracks, graphics and etc
Story
FF13
FF8
FF10

Characters
FF8
FF13
FF 6, 7, 9 and 10 (yeah, couldnt decide the 3rd place between these )

Battle System
FF13
FFX-2 (yeah, this game has a awfull story, but the battle system is perfect)
FF12


Now I need to buy a FF XIII-2 Though I still need lots of trophies in the FF13 to finish playing.

I have FF13-2 (jp version) and i'm at 59% completion for trophies but I don't have too much time to play games as I did earlier this last year. So I'll take my time.