I liked FF3 on the NES a lot, it's a real fun game!
On the SNES FF5 was the best one, it combined freedom of jobs (the most fun level up system) with quite a nice story, and good music.
FF4 was quite nice, as was FF6, but that one couldn't hold my attention and got boring, also has got way too many characters.
FF series overall: I loved FF7 the most, it's the best FF, has got the best/deepest personalities, and a very touching story. I still love the graphics, it's sort of nostalgic to me, and I own the PC one and a TNT2, so it looks quite nice.
FF8 was a story I also loved, except the ending, which I found quite vague, but the game (especially gameplay) wasn't as good as FF7 or FF9 (only talking about PSX ff's). The draw system also totally sucked, as do the characters: Squall and Zell are big time losers (no offence to FF8 lovers). Because: HOW could Squall let Rinoa alone for such a long time, she's the most beautifull FF girl ever.... and has got a very nice personality, she's an angel!!! I even got angry at Squall at certain points.
And I loved the way Seifer treated Zell: Chicken Wuss
FF9 was a very good story, with nice graphics, and I haven't heared the music throughout the game since my PC is too slow to emulate that in a decent way. But the story was really nice, a bit classical, because of the ending.
I haven't played FF10 or above, and FF tactics.