Well for me it was like this:
FF1. Classic old fun rpg
FF2. Very similar to 1, but little more storyline/characters
FF3-5. Started seeing nice improvement in storyline and characters.
FF6. Only one I have no played of the 1-14 series
FF7. Good, but I think a little over rated.
FF8. Loved the story, hated the combat system.
FF9. Favorite FF, awesome characters, great villian(and had VIVI, HE ROCKEDDDDDDD)
FF10. Really good storyline, liked the progression of story.
FF10-2. Charles angels in FF, did not like this one at all =.=
FF11. Played for almost 3 years, loved it, but played it over 5 years ago.
FF12. Good storyline, but to much desert, made it kind of dull for me.
FF13. Still playing it ATM on the PS3, like it thus far, better than some older ones, but not the best.
FF14. Still in the works really, will determine that when the official start charging us.

All it really comes down to is opinion, the thread itself is a empty personal statement on your own view even if others share it. But if I base it on my opinion to, I got to agree, it seems it has not been that great since 12, 13 and 14 I am still undecided on really, but both keep getting better to me.