Given time it could become a halo killer, sales wise, but it is a totally different game..
The single player isnt really anything special, but it does do good at glueing you to it so you cant spot till you died atleast 20 times before giving up. What ever story thats there(something about alpha squad and some kinda bomb and thoose locust freaks) does the game justice and goes along with the mood.
The multiplayer portion of the game is the better half. Either you win badly or you lose badly or you barely loose due to some BS. Matches are fun and fluid, sometimes fast, sometimes slow. The weapons are perfectly balanced and there are more ways to kill people than shoot them, my personal faviorate, grenade tag them with a smoke grenade to piss them off.
The graphics are pretty.......sweet......
The only flaw is that it has some framerate isues, ecpesially during cutscenes.
Also with smoke processing(all games have that problem i noticed).
The sound takes advantage of surround sound systems and digital sound.
Im getting tired of typing so ill make this quick, Gears of war is a must own for your 360 and is defientally the best game out for it at the moment.