I thought XIII's battle system was cool for a while. Then I started to hate it. I got to the point where it wasn't fresh and exciting anymore. It was just an annoyance to follow the exact same patterns repeatedly.
I also thought almost every character was awful. A few of them I just don't mind, but don't really care for. The story was positively not positive.
I didn't care about the linearity, really. I enjoy games with linearity... as long as I enjoy the story... or gameplay.
Even if XIII-2 is much better than XIII, there is no way I will ever give it a chance. Well, if they changed everything about it and killed off all of the returning characters immediately and gave it an entirely new setting and story, I might like it.
--
"Filthy lawbreaker, unhand that vending machine!" - Casey Jones