Final Fantasy
Final Fantasy is an ever expanding series, with most of the games appearing on the PS/PS2/PS3, with a few branching onto other consoles. Obviously, X is the tenth game in the series, focusing mainly on Tidus and his journey to get back to where he came from. X-2 is the first sequel to ever follow a FF game, and follows Yuna this time, as she searches for 'him' (Tidus), in the hopes that maybe she will see him once more.
the OST
Is the soundtrack to the game. This is all the songs, like 1000 Words, real Emotion, and the Japanese ones, like Kimi He and Hadashi no Kiseki. It can range from energetic songs that make you happy, to plain, beautiful ballads which can make you cry. It's got everything and that's what makes it special.
Why
I love this OST; it's one of the first games I ever played where it was partially the music that gripped me. Ever since the first introductions with Eternity: ~Memory of Lightwaves~, I knew I was going to love this game. Not just for the game itself, but the music sounded... so elegant. And then the opening sequence just blew me away. Playing through the game till 1000 Words, when the emotion came out; that song was so beautiful I was on the verge of tears. True, I've played a lot of games since with very touching, heartbreaking soundtracks, but this is the first one I ever played where the OST hit me so much, a lot like all of Square's soundtracks, so it's all that more meaningful to me.