I'm not saying X was a bad game, and I agree that the storyline was very good. It was the gameplay that let it down for me. I liked Tidus, but his voice did get irritating after a while - and I found him to be rather selfish "This is MY story!" Yeah right, anyone else involved in the entire game? Yuna? Yes, she's technically the saviour of Spira and he tries to take all the glory.
I just think that XII has redeemed what failed X.