Terrible graphics, terrible ai, terrible gameplay, especially the aiming and combat, and one hell of a cliche story. You can see every twice and turn miles away. The only reason it would be worth even considering a buy is if you want a coop experience, but there are way better coop games out there. My friend and I played it on Xbox and to be honest we should have just replayed halo 3 or reach, or even play through the gears of war's quintology and it would have been a much better time playing, and enjoying much better stories.
I top all that, the game gives you no challenge whatsoever, the puzzles practically solve themselves, and the combat is a joke.