Cheesy melodramatic story in a visually stunning package - if only they had hired a good screenwriter.
Contrast that with the stunning production values: hours and hours of animated video with good voice acting, beautiful visuals (both the scenery and the combat), great audio, a workable combat system, and what you get is a missed opportunity. If only they had hired a good screenwriter...
When it comes to RPGs, Bioware has set the bar with Mass Effect and Dragon Age, and while FF XIII can certainly stand on its own visually, it simply does not play in the same league regarding characters and story.
On the positive side, the game is really beautiful and while it is exceedingly linear, it is appropriately motivating.