that depends completely on what view of skill you have. I'd like to think CoD4 takes skill (mostly because I'm good at it). I know when I'm playing it I don't just run around and jump and shoot as fast as I can. see, your accuracy is significantly lowered when you try and pull shit like that, and combine that with any sort of lag in either your connection or theirs and you're basically relying on luck. So sure, I do run around a lot (but not jump, more like lay down), and yes, I do shoot as quickly as possible. but I'm constantly checking radar, if I have it, and I am factoring in the cover he's got and the cover I've got and all the different places we could shoot at each other from. I take a shot, and if I miss, I get down behind cover, and try and move to wherever he isn't looking so I can shoot again. Or I try and time it so he isn't prepared to shoot yet. yes, I am usually using a sniper (mostly R700, for hardcore search & destroy I've got an m14 w/ an acog, and for closer range I use an m40, no acog), but I definitely wouldn't say snipers are guaranteed wins, I mean, sure, they can be one hit kills, but you hold your breath to steady your aim (and it's slow to aim for the stronger ones), and if it's a moving target and you're moving too then it's really hard to aim right. you could get into position then aim but then you'll be sitting still for a few seconds at least and that means you're an easy target. even if you're in a building and covered then you have to worry about grenades and people coming at you once you get a kill or show up on radar. so yea, a sniper should be a guaranteed 1:1 kill/death if you use it right, but it sure as hell isn't a guaranteed 10 kill streak, even for me. (Actually my longest killstreak was with a shotgun, 25 killss baby, I ran out of ammo in the end and used my knife/someone else's gun for a few).
anyway it's more obvious that there's more to the game than jumping and pointing in the slow gameplay types, like search and destroy, or in the super-fast types, like sabotage. in search & destroy you've only got one life and even if you all die the other team can still lose if you played right. In sabotage a game really shouldn't last much longer than a minute or two, if your team is organized well enough. of course in both of them the shooting and jumping bits are prerequisites, but it is a FPS after all.