MAg is a PS3 game that is only online multiplayer. When you first play, it prompts you to pick a PMC(private military corporation). Until you reach the level cap at LV. 60, you can't change faction. This is a good way to make sure you are loyal to your faction and don't change to a different one.
The gameplay contains elemants of top shooters like Call of Duty and Battlefield. But unlike those games, you need a lot of teamwork. You actually have to work together, or you'll never win. In Modern Warfare 2, you can go all Rambo and kill a bunch of people by yourself, but in MAG if you try to do that all the time you'll just die constantly.
The player count reaches up to 256 in domination, but other modes are less than that. The map never seems overly crouded because each 8 player squad are in different places, not bunched together. The feeling of teamwork is rewarding. Also, if you go where your leader tells you, you will get a FRAGO bonus(extra xp).
Even though when you first start the game it can seem overwhelming, it doesn't take very long to get the hang of it. The whole sense that the people in your squad are the people you rely on and fight with the whole match (and you might meet them in later matches) is great. At moments this game matches MW2, even if it doesn't have as good of graphics. If you like intense teamwork AND a fun battle experiance, this game is for you