I have been playing COD4 for a few months. I started playing it at one of my friend's houses and it definitely wasn't love at first sight. The first time I played it I found the controls and found it to be extremely difficult. After being pushed to play it several times I realized it was pretty great. So great in fact, that it pushed me to go out and buy a PS3. Over 500 dollars later I had the PS3 and the COD4 game I just "Had to Have".
So for the game, you have the option of playing in game mode which takes you through a series of tasks and teaches you the ropes or you can go straight to multiplayer and play online with everyone. I prefer playing online. You can invite your friends to play if they have both the game and the system. Once you get to the online section you can choose the type of game you want to play. They have a game where you can play 12 players 6 to a team trying to kill the other team gaining more points. There are also other games involving protecting your flag and detonating bombs.
Overall I would recommend this game to everyone. I'm a girly girl and I love it. It is really fun and makes you want to keep playing all day long. I have only had it for a little less than a week and I have already played it a total of 12 hours. It's really that addicting.