All the complaints about linearity aside, I think one of the biggest problems with FF13 is the lack of a major villain for most of the game's duration. For those of you who've beat the game, we all know who the actual "villain" is, but the majority of the game goes on with the characters talking among themselves, and no real antagonist to fuel the conflict. The characters are completely removed from any of the political or social issues going on in the world since they're on the run for the entire game, so until the last 1/3 of the game or so, all the conflict comes from the characters whining to each other about their pasts.
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PSN - Aevio
BlackMageJawa - "I'm on a Goomba."