Easily FF6 for me on the SNES. That's the only one that I think is a true masterpiece. I'll love the characters/story/music in that game until the day I die. Kefka FTW!

this will be the most diverse list of any franchise guaranteed

VII>X>IX>XII>>>X-2>Crisis Core>VIII=XIII>>>>>>>XIII-2
Seven is just amazing story wise through and through along with best magic system and characters. X is very close in over all story epic but some of the dialogue falls flat, nevertheless combat is best in the series as well as best minigame(blitzball). IX is just very charming, story isn't as good as the other two but some of the character motivations are very noteworthy like Vivi and Kuja. XII is often misunderstood but had a really good main plot. Dissappointed me it didn't have much characterization for most. Combat system is maybe the second best in my book. unfortunately its lack of content keeps it from being as good as the others.

X-2 was a really good game imo, it gets a lot of flack for all the girly pandering. It had one of the best job systems ever, actually coherent story that expounds upon the original instead of just making new shit up. It only beats out Crisis Core barely as CC's story was amazingly done and delves deeper into the VII mythos, only the combat was a tad bit more lacking due to party/hardware limitations.

I have a love hate relationship with both XIII and VIII for similar reasons. They both lose sight of true purpose in the middle. Characterizations are total hit and miss (Good:Lightning,Fang, Sahz, Squall, Rinoa, Zell...... Bad:Selphie, Irvine, Hope, Vanille,Snow). I actually like XIII's combat system minus some very big hitches like not being able to switch characters mid battle. VIII's was decent yet that junctioning system equals totally broken.

XIII-2 is complete blasphemy. The game had little to nothing to do with the original story laid out by the first, instead utilizing the tired "Time Traveling" plot to mix things up. It comes off appearing like what we all know it is, a reusing of assets from the original and half assed updates thrown together quickly to try and cash in on stuff they already made.

Final Fantasy VII.  I was so completely engrossed in that game that when I got close to the end, I stayed up so late on a Saturday night beating the game that I actually overslept through my 4 hour Sunday morning shift the next day.  (Fortunately, my manager liked me and made up a cover excuse for me to keep me in his manager's good graces.  Other than that inicident, I was known for being very reliable, and later was promoted to a management position myself.)

I bought Final Fantasy VIII for my younger brother, and I never took to it.  Final Fantasy IX I liked, but it didn't seize my attention the way the NES/SNES Final Fantasy's and Final Fantasy VII did.  Final Fantasy X I would watch my best friend play at his house, and it left me with no desire to play it.  The voice acting particularly turned me off and left me longing to take a step backwards to text dialouge.  I also feel that way listening to Final Fantasy XIII cut scenes.

from what I played from the sony FF:
VIII>X>XII>X-2>VII>XIII

I much prefer the fast paced combat system in XIII/XIII-2. I absolutely hated it in VII and VIII when you would have to wait 30 seconds every time you used a summon attack.

Is the truth. 

Only thing Id change is FF9.  None of the post PSX FF hold a candle to the earlier games.

Shockingly I loved the gameplay of XII the best ( If you can even call it gameplay) but in terms of characters/story/music/etc. I'd have to say FFIX is my favorite. Then again those two are the only ones I can actually take seriously and get into playing.

Oh yeah, thought I would throw this out there. I've put about 10 hours into FFVI and I would go as far as saying I actually dislike it. *runs away*