To be fair, while it's not my number 1, I'll always have a very fond place for it in my heart; not only for the game that it is, but also for what it achieved, and for the landmark that it became.

1-FF VI
2-FF VII
3-FF X
4-FF IX
5-FF V

edit: None of than surpass chrono trigger, "The Supreme Turn Based RPG".

1. FF7
2. FF8
3. FF9
4. FFXII
5. FFX

1. FF12
2. FF9
3. FF7
4. FF14
5. FF2

List falls apart towards the end since I haven't played the other games too much >.

1. = Final Fantasy 6 (5p)
2. = Final Fantasy 7 (4p)
3. = Final Fantasy 4 (3p)
4. = Final Fantasy 9 (2p)
5. = Final Fantasy 10 (1p)

1. FFVII
2. FFIX
3. FFX
4. FFVI
5. FFXIV ARR

I must say though, tactics would be a solid number 2 if it counted.

1. Final Fantasy X
2. Final Fantasy VIII
3. Final Fantasy VII
4. Final Fantasy XIII
5. Final Fantasy IX

I haven't played the rest. 

FF 4 is my favourite Final Fantasy game, but I haven't played that many..

1. final fantasy 6
2. final fantasy 7
3. final fantasy 10
4. final fantasy 8
5. final fantasy 12

I wonder why FF6 is so poplar in oversea.
Of course 6 is amazing rpg though.

1 : FF7
2: FF10
3: FF4
4: FF5
5: FF9


I hope 15 will become Best Final Fantasy ever !