Even though it's not my favorite game, FFXII has the belt for me. 150 hours at least. I'll benchmark the others.
FFI: 50 hours. Didn't finish the game, mind you.
FFII: 40 hours, before Ii got fed up and spoiled myself.
FFV: Just got it. Clocked in like 20 so far
FFVI: 70 hours. Was trying to do side quests after finishing it, didn't work out.
FFVII: Played it around 8.5 times (still playing currently) Longest playtime was 130 hours.
FFVIII: 90 hours
FFIX: Around 90 hours, mainly because I left it on at night.
FFX: Can't remember, maybe 80-90
FFI: 50 hours. Didn't finish the game, mind you.
FFII: 40 hours, before Ii got fed up and spoiled myself.
FFV: Just got it. Clocked in like 20 so far
FFVI: 70 hours. Was trying to do side quests after finishing it, didn't work out.
FFVII: Played it around 8.5 times (still playing currently) Longest playtime was 130 hours.
FFVIII: 90 hours
FFIX: Around 90 hours, mainly because I left it on at night.
FFX: Can't remember, maybe 80-90

), next is FF: Dissidia which is 5 times. I'm not sure how long I've played it but, it took me more than a day to defeat Chaos the second time.