For my personally, FFVI has its place in my heart. Sure it had its imbalances in gameplay (that game is the easiest RPG in history when you use Vanish+X-Zone/Death), but it is part of the trio of games (Chrono Trigger and Lunar: The Silver Star) that pulled me back into RPGs. And it may have been a little pretentious as FF games tend to be, but there was still that grand feeling while playing through the game.
I liked FFIX the most next. I just like a stronger fantasy theme and designs, and while the story did have some "eh" points and not give much development to a few of the main cast, I still enjoyed it overall. I liked the light-hearted feel from it and the sidequests were mostly enjoyable for me.
Those are the two main ones, and I can't really think of where to place the others. I enjoyed and was addicted to FFVII for a while but for me, it's not one of my favorite RPGs, either. I honestly couldn't get into the characters and plot of FFVIII (they were just too angsty for me. I like to play games, watch movies, etc., to escape RL, not be reminded of my own pessimism or that of some of my angsty peers) and the gameplay system wasn't that fun for me. Either it was sit through summon spells all the time, or spend long periods of time drawing spells to keep stats high and that felt monotonous to me. The rest, um...I enjoyed them enough? Heh, can't think of much more than that.
Oh, yeah, and I hate Zeromus. I don't get it. The first time I fought him, I kicked his butt, but every attempt after, I got mine handed to me. Weird.