i have both of them but since cod4 came out i have been playin the heck out of hit. halo 3 is good because we don't know if their is gonna be another one in the series so it could last 5 year and with all the added levels u can buy but cod4 is super real and actually has a single player mode u would want to play, so which one would u pick and no fanboys, just pick one and back it up and keep it movin, NO HATERS