An astonishing package all around.
First off, the graphics and sound take this series to a once-thought unreachable level. The framerate never drops and levels like "All Ghillied Up" will blow you away with textures and shadow effects. The sound, as always, is the envy in the game-industry and features some amazing explosion and gun effects, as well as new radio conversations that help players immerse in the action.
But the technicals don't always matter, so how is the gameplay? One word: Amazing. Most of the missions open with a drop off by a helicopter or a satellite fixation on your position, and from then on it is intense and authentic, and sometimes you don't even leave your helicopter when something amazing or terrifying happens. The story is daring and gutsy enough to be taking place in this age of time in the Middle East, and, while it is all fictious, it seems like it could be ripped from the front page of The New York Times. While nothing can compare to the real action of genuine combat, the situations and objectives this game throws at you is extremely authentic.
Perhaps the best part of the package, the gunplay, is tighter than ever before and the best shooting you can find on any game, including Halo 3, BioShock, and The Orange Box. The A.I. is sometimes lacking or extremely smart, and sometimes you will be very frusturated by dying (many times), but it is worth it, because beating missions will give you an excellent feeling of accomplishment. I cannot say enough about how awesome shooting a gun is in this game, and when you have to take out a target from 500 meters away and see the results, you will definitely agree with me. Level design is awesome as well, and every mission will want to warrant more than one play.
Rounding off the package is the multiplayer that is on par with Halo 3's. While I still love Halo's multiplayer, COD4 throws in some nifty features like perks and customizable classes. The general feeling of multiplayer is great, and the classes seem very balanced. The multiplayer is more than "just the norm" and it just feels great playing multiplayer in this game, and it is better than Halo 3, no doubt.
Essentially, Call of Duty 4 is just an extraordinary game. Playing through the single player missions will immerse you in battles and war unlike no other game ever made. Multiplayer will become your new addiction. If you are an Xbox 360 or PlayStation 3 owner, you owe it to yourself to buy this game and see what all the fuss is about.