Camping in COd 4 is only a problem in Hardcore game modes.
No Killcam, no radar apart from UAV and even then, the majority of people use UAV jammer.
"And yes Halo 3 takes a lot of skill when you can just hit someone in the back of the head with your elbow and kill them."
Pretty much as going behind someone in COD 4 and shanking them. Its is actually harder to assasinate someone in Halo than COd as in Halo the motion sensors pick you up, so any half decent Halo player will turn around and pop you.
View