Halo. call of duty is fun but is a little too realistic. halo has powerups and other things that make it very fun. plus it is 10x harder to get a kill. if call of duty does have one bonus, it's how many more weapons it has. but halo does have more multiplayer gametypes and you can play with 4 people on one xbox 360. plus halo has alien weapons(needler, plasma rifle, spiker etc.) and customizable armor. plus you can break off turrets from their stands and move around with them. also you can hijack vehicles and forge. which is to take a map and design weapons and vehicles on it.
halo outa these two, there are definatly better games than halo but cod:waw is pretty lame, only good thing was nazi zombies ( which i admit is pretty awesome , even if you dont have the new maps which are much better)