I really liked FF13, the graphic and role changer were pretty good.
FF13-2 was ok, I didn't like how your characters are weaker than your monsters in the end. Also, Caius is like one of those Pokemon trainer with 6 Metapods and 99 HP Potions, he shows up way too often and his battles are annoying.
I still want to buy Lightning Returns, hoping she kick Caius's butt for real this time. >.>