I own
Final Fantasy I(Origins)
Final Fantasy II(Origins)
Final Fantasy IV(Chronicles)
Final Fantasy V(Anthology)
Final Fantasy VI(Anthology)
Final Fantasy VII
Final Fantasy VIII
Final Fantasy IX
Final Fantasy X
Final Fantasy XI
Final Fantasy Tactics
Final Fantasy Tatics Advanced
Final Fantasy adventure
Final Fantasy legend 1&2

I've played all of them and beat VII, VIII, Tactics and Tactics advance
But out of the ones I played (most I got to the final boss and was to lazy to beat him) I would say II, IX, and X were the worst. I didn't really like II for just the random battles pissed me off. IX tried to be like the older games but failed. X god... everything was bad except the graphic and I like VIIIs better :rolleyes2