What if the US occupation of Afghanistan but the Taliban are aliens who only communicate with grunts/guttural laughter/high-pitched Flea in THE WILD THORNBERRYS gibbering, and Afghanistan itself is the weapon of mass destruction, and it's all of the worst aspects of ALIENS (which is most of ALIENS) and none of the good but with zombies, and we just make everything after "The Silent Cartographer" a beyond tedious grind with copy-pasted corridors so we can shove this thing out the door on time.

tl;dr JockJamz MARATHON, or the BIOSHOCK to that game's SYSTEM SHOCK. Some interesting/compelling production design and gameplay dynamics throughout (hopping in a Warthog with a buddy is all-time and the assault rifle feels great) but otherwise utterly fucking dire even when playing co-op with a friend, not to mention grossly jingoistic and racist without the polish or design muscle to make it worth fucking with. Just skip to the sequel imho.