Final Fantasy X-2 initially hurt my love of the franchise, although I replayed the previous ones I own a number of times and coincidently after something like five years I played FFX-2 and concede the storyline is awful however I do not hate that game any longer. If you approach with the correct mindset it can be quite entertaining, especially the characters. Amazingly enough there is a plot buried in that nonsense of a story though, if only Square focused more on the Aeons uprising and Shuyin than Yuna in a bikini...
Final Fantasy XI I had little interest in as I dislike MMO for the most part however Final Fantasy XII was the nail in the coffin for me. The game had so much potential, yet fell by the wayside. The characters were interested - with the exception of a few (Vaan), yet saw little to no development. The storyline was intriguing, especially for myself, given my love of medieval/ancient political struggle, yet it had god awful pacing and was often forgotten completely and finally dungeons with lengthened to an unruly degree, turning it into a MMO dungeon crawl with an occasional clip here and there.
The fact Vaan was one of the worst main characters I have seen in quite some time also irritated me. I still cannot get over how often that game explicitly made a point to informing you how utterly useless Vaan and to a lesser extent Penelo were to the game. When one of the first few scenes has characters not even in your party, claiming they are the lead character, you know the actual main is inadequate.