A Retro Version of Modern Warfare...
I played the Campaign first: It was very interesting, but was like The Matrix on the confusion level. It's story involves a dillusional man named Alex Mason (Ironic, because there is a similar name in Red Faction: Guerilla named Alec Mason) as he tells of his adventures trying to stop The Union of Soviet Socialist Republics from destroying the United States via chemical warfare.
The graphics are excellent, at times even better than it's recent half brotherModern Warfare 2. I say half-brother since it's made by Treyarch and Activision and not Infinity Ward and the latter. You might be able to notice that Treyarch's Call of Duty is more gruesome, with limbs being chopped off. This was introduced in World At War, and has gone through some updates throughout the last two years. You will also notice that this game's blood physics are realistic, as where ever you shoot, blood will gush out of the body. It's pixel level is improved, as there are many more details with the soldiers. You will notice there are more enemies also (many more).
There are also a whole lot more vehicles...I am talking alot more. It's almost like Bad Company.
Multiplayer is almost exactly like Modern Warfare, though, you'd probably call it Modern Hippie. There are no vehicles in this game, but instead is replaced by killstreak rewards such as drivable helicopters for a certain amount of time, RC bomb cars, and ect. It also includes a playback feature so you can see the entire match from the eyes of yourself, other people, or even in third person. It is very useful for Machinimaniacs. I can already see some full blown movies that can be made with this simple yet powerful tool.
Nazi Zombies is the exact same of World at War, but there is more of a "Story" if you can call it that. I can't give
In all, this game is a very big improvement, and I can't wait to see what they'll come up with next.