I picked up COD4 kinda hoping for something not like COD and COD2. Both previous encounters with the COD franchise were very enjoyable indeed, but the element of a cohesive storyline was missing. You were bounced between Russian, English, and American campaigns trying to follow each smaller storyline to the end.
Boy was I pleasantly surprised with COD4. Blown away is more like it.
The plot of the game was very well done. The 2 story lines seemed to be going in 2 different directions at first, but later on you can see the 2 slowly merging in to one. The voice acting was top notch and lent itself to create a sense of empathy for those characters.
The graphics are superb...smoke, haze, everything contributed to an air of danger and realism in each environment.
I encountered a couple crashes during game play which, I am not sure were software or my rig locking up. I had one encounter where (in the Russian missile silo) I was being waved through a door by a character, I pass through the door and he just stood there waving me through. All with an "end of the world" timer counting down. I had to restart the level and try it again and it worked the second time.
The one huge gripe I have with the game is the single player game is waaaay too short. I think that I burned through the game's single player campaign in about 7-8 hours. I was left wanting more.
I have not played the multiplayer aspect yet, but I have never been a fan of PvP, but I might give that a shot (pun intended) soon.
In short I found myself immersed in COD4 like I have not been with a game for a long time. I highly recommend this game.