For me, X-2 is a lesson in pretty good gameplay, but rather shoddy storytelling. I liked it, though I do agree with Aulayna. The game was so easy to begin with, that any tactics to be used with the Dressphere system sort of melted away. Seriously, all you really needed was:

Dark Knight using Darkness
Dark Knight using Darkness
White Mage / Alchemist healing everyone

That would get you through virtually every main game battle, leaving more niche dresspheres such as the Trainer or Songstress gathering dust. The Warrior dressphere, while invaluable in the early game, is abandoned after Dark Knight is obtained at the end of Chapter II.

Besides from that, the Dressphere system was quite good, and brought back some jobs from other earlier games.

The sidequests were generally amusing sometimes and the minigames were cool (Leblanc's massage) though they did cripple Blitzball. While the game is pretty much easy, the Via Infinito did raise the difficulty triple fold. Chac, Concherer, Paragon, and Trema being utterly devastating bosses, not to mention the normal enemies at that time were tough as well.

The storyline itself though, was... decent. It's not terrible, but it's just loosely binded together.

Chapter One: Going round sphere hunting.
Chapter Two: Infiltrate Leblanc's chateau!
Chapter Three: Save the temples.
Chapter Four: Concert making.
Chapter Five: Defeat Vegnagun.

Chapter four being a great bore, going round with those commspheres.