As far as the main games are concerned...

FF X - I love the story, I love the characters, the way battle worked was a MASSIVE improvement over the last turn-based formulas. First FF I ever finished, but not the first I ever played.

FF XII - I am a huge Ivalice fan. I love that entire FF universe. The stylistic qualities of the game were amazing. The MMO-style active battles were a fresh look at the FF formula, and the sheer size of the overworld was magnificent. Still playing it now. At about 45 hours in I estimate I am about halfway through the game.

FF VIII - This was pretty cool. The story was a bit rough, but the characters were much better developed than in FF VII. You definitely feel like your choices as far as who goes where and what you do next actually impact the game. Stuck in the last area of the game because my Disc 4 is scratched and it takes about 5 minutes to load a single room.

FF VII - This game was great for its time, the second FF game I ever beat. The storyline was VERY well-written, but the characters were flat. I feel like I'm betraying myself by placing this game so high, not because this game was particularly bad, but because of the Compilation of Final Fantasy VII series. The game was not that good. It was nowhere near good enough to warrant an entire series of bad movies and bad spin-off games.

FF VI - I'm nowhere near finishing this game, but it's coming along well, and i can definitely see why people love this one so much. The story is pretty interesting, and I do like the intertwining stories running through it.

FF IV - Good story, good selection of characters. Fun game. Still haven't beaten it, Zeromus is way the hell too hard.

FF III

FF V

FF I

FF II

FF IX - Played a little of it, didn't really interest me.

FF XI - Was already uninterested when it came out. Heard about it from people afterwards and decided that I was not going to touch the thing.

I bought FFIII for the DS...looks great in 3D, and the FMV is cool, but it just feels so old...and I got sick of the random battles...I'm not a fan of randomly spawning battles.

So yeah, I dunno if I'd recommend FFIII...but if you like the other FFs, you'll probably like this one...I prefer RPGs where you can see the enemies before you fight them.

I think we should be able to count the "spin-offs" like CC as well...it's just as much a legit game as the main series...

Tactics and Tactics Advance I thought were amazing games.

Crystal Chronicles was good, both as a single-player and a multiplayer.

X-2 was okay. The platforming aspect was a nice addition. The "dress-up classes" thing was... yikes.

Mystic Quest was god damn pitiful.

If FFT was allowable on the list, It'd be my #1, and Mystic Quest was better than 8 and X2.

1. Final Fantasy VI (SNES)
2. Final Fantasy IV (SNES)
3. Final Fantasy VII (Playstation)
4. Final Fantasy X (PS2)
5. Final Fantasy (NES)
6. Final Fantasy VIII (Playstation)
7. Final Fantasy IX (Playstation)

Mistic Quest was (pretty) bad but I would still have it on my list at (roughly) the same sport as Final Fantasy X ...
After Final Fantasy XI I haven't played a single Final Fantasy game because I think the quality and focus of the series has been lost ...

Ah, tripping the Final Fantastic... it's kind of unfair to compare the games, because the technology has changed so much, so fast. Here are my own favorites, loosely grouped by time-period:

Best of the early 1990s: FF 4. I didn't run across this until quite recently, actually, but it's impressive how much of the Final Fantasy magic is there. Addictive, immersive, and a great storyline, the multiple plot twists were never forced or artificial. Cecil grew on me as a character, and watching him mature and deal with the very tough legacy of his past was a delight. 

Best of the late 1990s: FF 7. Deepest characters and RPG storyline of the 1990s. The visuals have aged a bit, but the underlying story, a kind of late 1990s eco-fable, is dynamite. Cloud, Tifa and Sephiroth - damn, what amazing characters. Certain parts of this game still get me misty-eyed (Aeris! noooooo!!!!). Also remarkable: the amount of subtle humor and satire in the storyline - corrupt politicians, scheming scientists, etc.

Best of the early 2000s: FF 10. Great characters and storyline - yeah, yeah, I know the US voice acting was... uneven. (Yuna's closing speech: *wince*. Say it ain't so, Yunie!). But when the voice actors are "on", it's terrific. Great art design, marvelous environments, sturdy battle mechanics, and a surprisingly deep story about guilt, family and redemption. Tidus and Yuna are magical together. Wish Rikku and Kimahri got more air-time, though.

Best to date: FF 12. Best. Final. Fantasy. Ever. It's that good. Reasons: (1) strong, independent female characters. (2) open-air gameplay and presentation, the gambits system works beautifully. (3) stirring sound-track and some of the finest voice-acting ever performed (both Japanese and English versions are marvelous, but Gideon Emery and Nicole Fantl deserve some kind of Nobel prize for their voice-acting). (4) geopolitics of storyline. Oh, is the story ever complex - layer upon layer of betrayal, intrigue, revenge, Empire, anti-imperial resistance, which builds and builds to the conclusion. It's also the first videogame in history which has a credible interracial/cross-cultural romance at the heart of its story. Just amazing.

Shrug, feel free to put them in, some people have happily ignored my requests, besides, they were selfish, out of lack of experience. If we allowed them, I would only be able to add X-2 and Mystic Quest in, I'm not a SRPG player. Nor did I play chronicles.

FF10 - Beautiful story, world.

FF06 - So epic. I never thought 16-bit could tell stories like that. 

FF12 - Story was BS, characters sucked.  Still took 100 hours of my life with ease. 

FF04 - I almost never finished this cause I started on FF06 >_< 

FF11 - Oh wait I don't think this one counts, but I waited 8 hours in Qufim for a group >_< 

FF07 - I hated the first move to 3D, I hated it like I hated Metriod Prime.

FF08 - Couldn't finish this one either.  I played the card game minigame more than the actual story.

FF09 - Got halfway through but then the horrible art finally got me.

VI - the best story, the best characters, the best enemies, and revolutionary for it's time

IX - tons of tributes to the oldschool FF games, I just loved everythign about this game.

IV - second best story, second best characters, still awesome.

X - pretty good, I liked the graphics, but Tidus was such a baby it pissed me off

III - great for old school goodness

I - great for it's time, kinda dismal now.

XII - In retrospect I didn't HATE it, I just got bored of it. My Gambits won the entire game for me. It was nice to get rid of random world battles and the voice acting was by far the best in an FF game. Vaan was a pussy and next to useless in the plotline (which was overall pretty pathetic) though. *sigh* This game was unfortunately were I realized I don't need to buy any new FF games in the main series anymore, as I have no more interest.

VII - okay, I really don't like VII. I know that a lot of people love it and see it and scream OMG greatest game ever, but I really have never been able to figure out why. Cloud was generic and practically emotionless, Tifa was just there for a pair of boobs, ugh I really dislike the characters in this game. Sorry, I know I'll probably be attacked for this but man I really dislike it's characters.

VIII - the only thing worse than VII (Squall = robot who is in love with a Tifa clone who can't fight).

II - the crapyness of this game speaks for itself.