FF 13 was for me the single greatest let-down in gaming ever.
What made 7, 8, 9 and 10 great? Decent plot, by and large-great music-easy to grasp combat mechanics. But what drives them all is their story-the characters, their development, a bit of humour every now and then and all wrapped in gameplay that is addictive, reasonably simple and fun.
13 lacks all of these. Can't fault it for looking good, but it feels like that's the only thing they were going for. The writing is TERRIBLE. Beyond description. All the characters are boring and one-dimensional except Sazh, who is under-used, but suffers the problem of having to remind the player at regular intervals that 'Pulse L'cie' are enemies of cocoon. To the point where it should be/is his catchphrase. Vanille is the most annoying person on the planet. Hope is the second. Fang is pointless. Lightning is boring. Snow is a moron. And now that they've moved away from text blocks for speech and can no longer express emotions with "!", ALL the characters make ridiculously over-loud gasping noises to express EVERY emotion, to the extent that if you closed your eyes over certain sections you'd think you were watching porn.
On top of that, the story makes no god-damned sense. What the hell is cocoon? What's a fal-cie? Why should we care? The idea of 'slow-release-of-information' means that for hours into the game you have no real idea whats happening, and the "why should I care" is never answered. I never cared. I was almost always bored.
Other criticisms-since you can customise your weapons and make them ridiculously powerful, theres literally no point ever changing weapon. You get so many attacks in a round it's hard to see how much damage you're actually doing. The crystarium is the sphere grid without the freedom, and it pointlessly makes up words like "Crystogenesis" to explain the process by which you advance along the grid. As if ANYONE CARES!! ITS A LEVEL-UP MECHANIC!. No side quests, except that stupid massive endless plain where you can hunt, like it literally says "welcome to token side-quest area. Enjoy". Not being able to control your party was a terrible idea, because they're stupid. For the first paradigm shift PER BATTLE making everyone do a silly little pose WITHOUT PAUSING THE ENEMY. Making it so that if the character you control dies, you lose-who is usually the first person the enemy all attack at once, since they're in the front.
Put short, I would never have bought the game if I'd known how bad it was. I would never have bought the game if it wasn't Final Fantasy, the latest in a line of what have largely been fantastic games, and the biggest gap between the great game I expected and the sheer pile of crap one I got. I sold it without finishing it. I do not care how it ends, and that is the greatest failure a story-driven game can have.
Worst game EVER.