Final Fantasy : Yes, 3 times, soon to be 4th
Final Fantasy II : Yes, 2 times
Final Fantasy III : Yes, Once, retrying on the DS now.
Final Fantasy IV : Yes, 1 time.
Final Fantasy V : Yes, 1 time.
Final Fantasy VI : Yes, a proud 7 times.
Final Fantasy VII : Yes, a saddening 1 time. Playing again for a perfect game file.
Final Fantasy VIII : OMG YES YES AND YES! Proud and somewhat sad 25 times. And have 2 perfect game files.
Final Fantasy IX : YES! 4 Times.
Final Fantasy X : ...Don't remind me.... Yes I have twice, each being a near perfect game except for when my first data got deleted via washer
Final Fantasy X-2 : Yes. 2 times.
Final Fantasy XI : Can this be beaten? LOL Uh I PLAY IT. I don't think you could ever quite, BEAT this game.... and if so what would we classify 'beaten' as..
Final Fantasy XII: Yes, 1 time. Sadly I won't try doing it again unless for a perfect game.

Spin-offs
Final Fantasy Tactics: Yes, 1 time, playing right NOW on the PSP
Final Fantasy Tactics Advanced: Yes 1 time.
Final Fantasy Tactics A2: Yes 1 time.
Final Fantasy Adventure : Can't remember if I did...
Final Fantasy Mystic Quest : Never finished.
Final Fantasy Crystal Chronicles : I played with a friend, 1 time.
FFXII Revenant Wings: Almost done.
FFVII Crisis Core: Yes, 1 time.
FFVII Dirge of Cerberus: Yes, 2 times.
FF Chocobo Tales: Yes, 1 time.
FF Dissidia: Yes? In terms of story I have, in terms of leveling all the characters to 100. No!

You missed: Dissidia, Tactics, Tactics Advanced, Tactics Advanced 2. Legend 1,2,3, and Before Crisis,