I agree with a lot of what Yars said.

I don't mind linear games. In fact I infinitely prefer them to the wide open worlds of games like GTA. The problem with FFXIII was, as many have said, the path you took was literally a straight line. Run down this corridor, get a cut scene, fight a boss. Repeat. There was absolutely nothing else you could possibly do in that game pre-chapter 11 except progress the story. I like sidequests. I like intricate caves with branching layers. I like (limited) exploration to discover hidden areas. All as an aside to the main story which is directly in front of you. FFXIII had none of that until the very end, and even then it was just boring old mark hunting.