Personally I think FFX-2, FFXIII-2, FFXIV-1 were only bad games. Spirts within.... wasn't FF but could of been betteroff as something else or even improved apon.

Best FF games in my order (will not do them all)
FF6 (good story, good battlesystem)
FF7 (good story and balanced & new battle system)
FF5 (Tons of Jobs..!)
FF12 (Amazing Story and Music and overall art design)
FF10
FF11
FF8
FF9