I love all the people that claim one game in particular in the series was amazing or whatever and then say another one sucked (I'm speaking about everything post CoD3, for the record). Newsflash guys, all of them since CoD4 have been EXACTLEY THE SAME GAME. Slightly different campaigns, microscopic tweaks to gameplay, and a few new increasingly game-breaking features each time, but fundamentally the games all have exactley the same gameplay. Raging about one and then praising another makes absolutely no sense.
As for my view, I can sum CoD up in one word: generic. I'm talking core gameplay here - you shoot the person, he dies, rinse, lather, repeat. That's literally it. Grenades and melee attacks have exactley the same effect, and all the guns do exactley the same thing - they all make the enemy drop dead. This isn't Halo, where all the weapons and equipment have unique functions and there's a clear set of game-specific tactics, nor is it TF2, where each class's gameplay is fundamentally tailored to a different mission. It's just *boring.* I will give the games some credit, what's there has been very well polished - it's just too bad there's nothing much there. It's like they made the basis for a fun FPS and were going to put some cool game mechanics on top of it (i.e. Crysis with the suit options or Mirror's Edge with the parkouring), but just left it at that basis.
To the game's credit, the singleplayer campaigns have a few cool set-pieces and bits of scripting (and MW2 in particular takes you to a few cool locales), but the whole thing feels very much like a rail shooter. Go here, shoot this enemy with this weapon, get on this turret and shoot when and where I tell you, hide behind that bush, use your grenade launcher now. It's too scripted, too linear, and the pacing is too rigid. Too cinematic, in a way. It's fun once, but after that there's absolutely no replay value.
Multiplayer is an unmatched disaster. In addition to the game being extremely bland - the afformentioned boring gameplay, the lack of any real objectives or teamwork, the utter forgettableness of most of the maps and matches - it's also horrendously broken. Ever since the game-breaking helicopters in CoD4, once one side gets a slight edge or has one really good player, the entire game tips dreastically in that team's favor. The horrible map designs don't help - you spawn out in the open to be killed by airborne enemies two seconds later, enemies spawn right behind you with startling frequency (lack of any clear "sides" on the maps), the layouts don't ecourage teams to stick together but instead everyone to run off in their own direction. Then I compare it to a game like TF2 and the whole thing seems even worse.
Normally I wouldn't go on such a big rant about one generic game, but when one gets more popular than Christ without actually doing anything while hundreds of vastly superior games get overshadowed, it's hard to not want to take the piss out of it.