I think the best FF in terms of actually being a game rather than a semi-interactive story is FFXII. However, it just doesn't cut is as a FF since the series is all about epic stories and memorable characters. That said, FFXII is quite an acquired taste, like red wine or something. At first you might just think "What the fuck is this?" but I've played it through twice - just to give it another chance after being underwhelmed the 1st time - and I really enjoyed it the 2nd time and started to really see where it had succeeded rather than where it had failed.
Well, my list would go like this. It's based on how much I enjoyed the story and the setting, mainly. However, in some cases the story was nothing special but the character customisation was great or there was something else to make up for it.
FFVII
FFIX
FFVIII & FFXII (both fall down in story/characters but have other things to make up for it)
FFV
FFVI
FFX-2 (Purely because of the battle system, relative openness... And Paine.)
FFX (I really hate this game but there's a lot more to it than the following FFs)
FFIV
FFII
FFIII
FFI
See, to me FFVIII is where the series went a bit shitty. I really didn't like it at the time, but then FFIX came out and made up for it. Though when X came out I realised that FFIX was just a brief respite from the nosedive the series was taking. The thing is, FFVIII actually grew on me and now I can actually appreciate it despite it having a very badly-paced and dodgy story. FFX is yet to grow on me. I put V higher than VI because, although VI has a better story and better characters, I find it really drags on. I love it, don't get me wrong, but FFV just about beats it for me because it's much more playable. I didn't include XI because it's not fair to compare it. I played it a lot and really liked it but it's just too different to compare. Same goes for Tactics, though I'm really not a fan of the FFTA games at all.
As weird as it may sound I always thought FF8 was the best.
I liked the storyline the most because it was more of a love story than save the world from the bad guy story. Don't get me wrong... every RPG has that element to it, but the way it played out felt like it wasn't focused around that. I love the fighting system, the chracters, and everything else.
Memorable characters
Complex story
Great turn based gameplay
Funny and Sad moments
A lot of side missions and secrets to find
A very long game if you play it to it's fullest
You can go on the date with Yuffie (maybe this is just me)
It's the only final fantasy game you know all then names of the characters. Come on, you know it's true.
FFVII will always be my favorite.
My second would would be a tie between VI and VIII......for now.
To be honest I'm quite happy there are others than like FFVIII as much as I did. I always felt like there were no others that thought FFVIII was even a good game, much less the best FF of them all. 8)
I have a raging hard-on for class-systems.
1. FFTA. My introduction to class-systems. I have a moogle who's mastered every ability possible. Other than getting all the mythril weapons (missing the damn Great Sword) I've pretty much 100% it. One 300+ hour file and another 100+ hour file.
2. FFV. Loving it so far. Still haven't beaten it since my DS charger crapped out.
3. FFXI. I just started this a few weeks ago. It's tons of fun with my roommate.
4. FFT. This game kicks my ass. I still haven't beaten it. I think I'm close though. >.<
5. FFX. Story was alright. Loved the sphere grid despite the fact that in the end everyone was identical. Game would've been perfect if everyone had they're own sphere grid and stat caps.
6. FFI. Made it to level 99 just getting lost in the last dungeon. Must've fought the Lich King 20 times. XD
7. FFTA2. Horrible letdown. FFTA was in every way greater...>.> I still kinda liked it though.
8. FFIV. I've started it 3 times and due to various circumstances I've had to restart. I liked it enough while I was able to play it. Haven't gotten around to starting it a 4th...
Those are my faves. FFXII was kinda annoying. Vaan and Penelo, despite being the main characters, had the LEAST amount of effect on the plot. Balthier and Fran are that game's saving grace.
Final fantasy 9 is still my personal favorite of them all. No need to grind for hours upon hours for mastered materia like in ff7, and no need to play the card game for god knows how long in ff8. Everyone remains unique, unlike ff10. I did like ff10-2's system, where you could adjust your characters on the fly in battle, but sadly most of the missions are just so boring...you're only doing them to get 100%. Thankfully though with new game plus you don't have to do them twice. I don't really like the 4th, although they did make Rydia...;)
I'd also like to add that I personally found the side quests in FF9 more fun and enjoyable then other ones. And of course, the rewards are oh-so worth the time you put into them.
My top 5 would have to be...
1. FF the orginal is classic
2. Dirge of Cerberus FF VII loved the story (mostly because I'm a Vincent fanboy)
3. FF VII overall great game
4. FF Tactics War of the Lions(psp version) gave me something to do during class
5. FF VIII liked Squall and overall was good