As someone who considers himself a huge fan of the series, Final Fantasy X is the hardest one to place. Like you, I really hated it at the time. Some of that I attribute to it being different; some of it it I attribute to it not being that great.
Over time, my opinion has completely turned around. Though I still believe it is a poor Final Fantasy game in most regards (a recent attempt at playing it again confirmed that much for me), there are elements about it that I cannot ignore. The setting, cultures, and music are all amazing, for instance. Most of the characters are decent too! If I ever forgive it for its linear design and boring, it’ll be from that story.
The story makes the game. In typical FF fashion, we have a pretty serious romance plotline, but this one becomes the forefront of the game. Over time, you see their relationship bloom not as an aside to what is happening, but as the main point. I won’t spoil the ending in case anyone is reading this who hasn’t experienced it, but it was a game changer for the entire game.
Sadly, X-2 was abysmal and had a story that I felt was making fun of me for the reasons I liked the original’s. Oh well!
In discussions I have had with my friends about FFX, the game almost always has a strangely mixed reception. Those who absolutely loved it often admit it still had some glaring faults. Those who absolutely hated it still praise it for being one of the best in the series in certain regards.