I honestly don't feel that the comparison between XIII and X in terms of linearity is justified. XIII is way, way more linear than X was. I admit that X was linear, both in story and in the path you took along it. But it was far, far more open than XIII is. You had to go from A to B to progress, but you could at least move around while doing so.
Remember when you first arrive in Spira? You land in the water and start to explore this strange new world. There is only one way out, but you can move around, find treasures and hints about the world before you take head to that one way. In Kilika Woods, or the Besaid path, there are multiple paths to take, offering some freedom of control for the player.
In XIII, there is no freedom of movement at all. The corridor is so narrow, your party couldn't even walk side-by-side along it. There is zero exploration for the world. There is no way to explore, let alone rewards for doing so. There is, in fact, no reason to even let you have control outside of combat. There is a straight path, you travel it in one direction, and you get in the same number of fights whether you have control or not.
Maybe FFX had a one way corridor for 90% of its paths, but at least it wasn't a straight line. Even the Mi'hen Highroad had offshoots to explore. It also had some width to it, allowing your characters to move side to side if they wished, to allow NPCs to pass by the characters, or random battles to break up the monotony.
FFXIII just feels wrong. The path is everything. Fights are structured into the path. You see them coming from a mile away, and you will fight the same number of enemies no matter how you choose to proceed (although, really, you don't have any options about how to proceed). NPCs also are built into the path. There is no life to them. They feel like the ruins and statues you pass. Each one structured so specifically into the corridor that you feel like they'd die if they had to move. And no matter how brilliant the main characters sound, everyone else is stuck without voice acting and without any compelling dialogue.
FFXIII doesn't feel like an RPG, it feels like a rail shooter that has its foot on the breaks. The world outside of battles and cutscenes just doesn't exist. A battle and cutscene montage would be preferable.
