I like 3 & 5 for their job systems.
FF1 has a weak story IMO. (Granted, it is a pretty old game and the amount of text space available back then was limited.)
FF2 has a weird "leveling" system and a very high random encounter rate.
FF4 was fun for me for one play through. I have no desire to play it again though.
FF6 was pretty fun. No real complaints about it.
I never actually finished FF7 because of how boring I found it. Whatever the appeal of it is, I don't see it.
FF8's combat system is annoying. Drawing magic is tedious and leveling up is actually not a good idea. :/
I've never played 9-13.