Pros: Multiplayer Gaining ranks keeps you playing Singleplayer is fun and addicting
Cons: Takes a couple of missions to really get into the singleplayer
The bottom line: CoD4 is a magnificent game which will test your reflex skills and your cunning. The multiplayer is unsurprisingly the most fun I've had in an FPS in a long time.
Call of Duty 4:Modern Warfare took a huge fall away from the tree where Call of Duty one, two, and three landed. To start off, we're now dealing with modern warfare instead of World War 2. Although... is this a good thing?

Yes!!!!

Sure, there are tons of World War 2 FPS shooters out there, but there are also a lot of modern warfare games which take place in the Middle East. The Call of Duty series has always been at the very top of the WW2 First Person Shooters, and there's no exception with its modern warfare title. It is by FAR the best modern era first person shooter that I have ever played.

Singleplayer:
The singleplayer starts out as you being a new recruit for a specialized team for the British Forces. You pass through a series of shooting, knifing, grenade throwing, shooting through barriers, and sprinting tests. How well you do on the very last test weighs on what difficulty you're allowed to choose. (But don't worry, you can do this as many times as you want)

The next scene, you're on a helicopter in heavy rain, about to board an Russian freight ship. The graphics are amazing on this scene by the way. I'm not going to get into details about the missions, but each one is fun and interesting in its own way.

Different Types of Singleplayer Missions:
During the campaign, you'll be submitted to a variety of missions.
There are sniping missions where you're given a Sniper rifle and a short ranged weapon. Stealth missions, where you're given all silenced weapons. All out brute force missions, where your knife will come in handy :) Even when you think that you've finished the game, there are a few extra missions to complete. Such as rescuing a hostage from an airplane, and jumping out just before a bomb goes off.

Multiplayer:
Now this is where Call of Duty 4 gets interesting. Well... more interesting. The servers max at 64 players, but it is very simple to find servers with ALL sorts of numbers of people playing. Once you find a game in the standard "find a server, double click, have fun" menu, you're ready for some killing.

You gain ranks as you kill people, plant bombs, defuse bombs, complete in-game objectives, and so on. The ranking is based on a 55 level system. With each new level, new objectives are unlocked, new guns, new uniforms, different perks, and new gun accessories. These new guns will come in handy when you join a server of all level 55 people.

But don't worry, even though you're a level 1 n00b, your ol' fashioned M16 is still one of the most powerful guns in the game. Infact, it's still the primary weapon I swear by. However, they will have an advantage on you when it comes to perks.

Perks are different options you can use to customize your soldier. You can pick a perk that will make you invisible on radar, or allow you to carry 3 grenades instead of 1. My favorite perk is Last Stand, where when you get shot just enough to die, you fall to the ground, pull out your pistol, and are allowed to get a few extra rounds off at the guy who shot you.

The game will grab you and never let go. That is how good this game is. You'll meet friends, kill enemies, and have a great time doing both. Hopefully this game will be game of the Game of the Year for 2008.