8 - in my opinion - got a bad rap only because it got rid of the equipment system - and added weird upgrading & parts collecting.
IMO - the game has a huge amount more depth than many of the other titles. True too - the character development of Squall is a masterpiece. Too bad we haven't seen much else that ranks in the same league of the FF's with a real storyline (read: Not released for the PS2 or mainstream audiences. )
6 - is my all-time favorite, followed by 8.
But if you want to go all-out hardcore -
FF5 - jobs system OMG! So that's where Tactics got that from (3 actually, but whatever)! *drool*
Seriously too-bad that the 2D ones aren't remade into eye-candy ... with a storyline. Even a remake of those oldies would be better than 99% of the crap released for consoles today.
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For my FF "vitals":
1) FF6 owns all. If you like 7 - you haven't played a real FF title yet.
2) When you've played as many as I have, you don't have a favorite character. See below:
Black belt/master - try em barehanded - FF1
FF2/3 - Didn't play (much)
Rydia - Poor girl ... she took having Cecil killing her parents so well - FF4
Faris! - Cuz she's a pirate! YARR! - FF5
Gogo - What can't you love about the guy who was EVERY SINGLE CHARACTER IN THE GAME? - FF6
Cid - Pure badass. - FF7
Quistis - Sure, call me a Treppie. Plus, she's got a whip - and those boots ... ahhh!

. FF8,
Freya - She was pwncore - coolest rat you'll ever see. FF9
FF10 - None of the above.
FF11 - LOL!
FF12 - Never touched it.
Agrias - Gotta love her holy knight attacks. FFT
Viera Assassin - Fairy shoes + Masamune 100 = the coolest 1 hit kills you'll ever see. FFT-Advance
Though if you forced me to pick ... I'd need to say Quistis. Those boots ... boots ...
3) Kefka - FF6. Gotta respect.
4) Diablos - FF8
5) FFTactics, FFTAdvance. FF6 - I had a full set of economizers for my entire all-L99 team - all picked off Brachosaurs. You go figure out how long that took to do. It was so bad - I could finish final Kefka with a single person. I even leveled Umaro. XD
6) Getting through the ice cave for the first time on original FF on the NES - without LIFE - and - as a noob. ( Aww man ... )
7) What? Clips? What's that? Real FF didn't have clips.

But -hmm- *thinks thinks thinks* something wtih Rinoa or Quistis.
8) Final Fantasy 6 with modern graphics. Seriously ... needs ... to ... be ... done ... like last year.
9) FF Tactics. Honestly, is there a better FF-realm uber-long-gameplay game out there? Hell no. Half-hour-long battles FTW!
10) I don't think about this kind of stuff anymore, but - Quistis man - Squall's a blind ass dumbass WTF's his problem.