1. FF6. This is the game that makes me feel at home. I love everything about Six, even if it's one of the easiest games in the series. I love the setting, the cast, the story, the music, the visuals, the battles, the way every character is customizable but still unique after you've sat there and grinded them all to have the same spells. I love this game. It will always be my favorite. Plus I had a huge game-crush on Terra as a little kid.
2. FF8. Again, the game is really easy, but I actually fell in love with FF8 before leaving gaming behind for two years. 13 not withstanding, it was the last FF I played, and I was genuinely surprised. As a child I hated Eight, and I admit that the cast was aggravating initially, but by the end of the game I had been won over by the music, visuals, fun Limit Breaks, setting, and yes, Squall and Rinoa did indeed manage to win me over in the end. That damn scene on the Ragnarok. That whole damn space sequence.
3. FF9. This is the only FF with which I have literally no complaints. There is, mechanically, nothing wrong with FF9. I would venture to call it the perfect FF. Nothing about this game has ever made me angry. It only is not my number 1 because other games draw more powerfully on my emotions. Otherwise, Nine is great. The music, the story, the battles, the systems, the villain, the everything. Nine is as near to perfection as any FF has ever come.
4. FF5. The other great FF, in terms of mechanics. 5's Job Class system is, to this day, my favorite iteration in any FF ever. It was a great, light hearted game which proved to be surprisingly grim at times. It brought us Gilgamesh, Bartz, and Faris. The only complaint I have with Five is Krile. She is the worst kind of Mary Sue, and I go out of my way to kill her before even Neo ExDeath can in the final battle. Otherwise, FF5 was a great game.
5. FF7. I have some very fond memories of Seven, and will always be a closet fan of Cloud, Aerith, Tifa and Sephiroth. Seven built on a lot of the good things in Six, and brought FF into a more mainstream popularity. The game had lots to do, and it was really a solid play. That said, it has, hands down, the absolute worst visuals in the series. Those crappy visuals are the only reason I support a remake of it sooner than Six and Five.
6. FF4. The Archetypal FF. Four set the trends of the series. It introduced us to a "brooding" protagonist, who struggled both internally and externally. It focused its plot on its characters, had crazy twists, gave us characters with defined job classes, and was easily one of the most epic games of my childhood. It introduced me to my favorite villain in the series: Golbez. It had three world maps, and the GBA version gave us ten PCs and a lengthy bonus dungeon that occasionally fleshed the cast out further.
7. FF1. I just like this game a lot. Whether that be because it is so iconic, because it offers me freedom, because I love the FF1 mythos a ton, or what, I can't say. I just really like FF1.
8. FF10. Ten's story was pretty amazing when it came out. The ending blew me away as a kid. I liked that the Sphere Grid was a compromise between the two systems- job and set-job characters. Visually it was awesome, and the only downside was the lack of a real world map. Also, the Ultimate Weapons required Herculean reflexes to get.
9. FF12. I loved 12's beginning. The ending blew in my opinion, and I hated that Vayne and Venat were such hypocritical villains. Twelves battle system is the epitome of all I hate about non Strategy non Action JRPGs. It was just so dull for me. Even so, the Marks were exciting and challenging on occasion, and there was a lot to see and do, which, I think, explains why I felt so disconnected from the ending when it came about. All told, though, 12 was a good game, inspite of a few beefs I had.
10. FF3. This game is here mostly because it beats out the other two remaining FFs for me. FF2 and FF13, which I consider polar opposites and good examples of how neither side of the "linearity" issue should be treated as good. FF2 was too non-linear, and it became a hell of a game to finish. FF13 was too linear, and I didn't get to explore even a fraction of what I wanted to. I liked both of those games, but 3 beats them out by a country mile. 3 Gave me jobs, world maps, dungeons and catchy tunes. The DS version was all around a blast. My only complaint with 3 is that, looking back, it is a very short game.
Bonus list!
Spin offs!
1.FFT
2.FFT0
3.DDFF
4.FFCC
5.FFMQ
6.FF4HoL
7.Anything Else.