Right, I'll guess you mean Final Fantasy XIII as the others are not on xbox.
It's very hard to describe, you will either like it or you won't. It actually looks better on ps3, but the xbox version is okish really.
It is very "walk in a straight line and fight monsters by pushing the x button a lot". The later battles though, you need a strategy or you will get creamed.
One of the characters in it has been described as the most annoying character ever in video games.........but I quite liked her.
In all, it's really more like an interactive movie, moving from one cut scene to another. I enjoyed the play through, but many didn't.
My current game on xbox - I am just about finished with Skyrim, which if you like that sort of thing is the game of the year surely