The only thing I really don't understand about X-2 is Spira's mood change. Spira had been living with Sin for a thousand years, with no true respite from the spiral of death. Yet, suddenly one summoner defeats Sin and lives, and everyone accepts that the spiral has ended? It had only been two years, and despite living in a world that is defined by despair, no one thinks that Sin might return, might be reborn once more? The change is too swift, IMHO. Spira had lived in shadow too long to be so accepting of the light.

X-2 in no way made X worse though. They're seperate games, and even if they take part in the same world, nothing compels you to play X-2. Even if you have played it, I don't see why it should change your perception of X. If you don't like X-2, fine. Forget about it, and just focus on the game you really enjoy.