FF1 - Last Game Ever
FF2 - Story
FF3 - Gameplay
FF4 - Story
FF5 - Gameplay
FF6 - Story
FF7 - GRAPHIX+Story
FF8 - BETTERGRAPHIX+Gameplay
FF9 - Story
FF10 - HAAAAA-HAHAHAHA (Story)
FF11 - MOO
FF12 - Gameplay
FF13 - LOL (Story)
FF14 - MOO+
Seems to be kind of a pattern, but ultimately you like the FF games that cater more to what you like. Either the focus on good story/characters, or the focus on good gameplay/customization.