They both came out 2010 so they should be worth around the same in stores right?
Not necessarily. What I mean is that his mother got him God of War 3 for his birthday and he instantly traded it in for an out-dated game. The multiplayer community for Bad Company 2 is dying and the singleplayer is not too great at all. He probably would've had a better time with God of War 3, granted he's not too scared to see someone's head get ripped off and then later on he would have had more money to buy Battlefield 3 (with or without the trade in). Now he's stuck with an old, multiplayer-centric game.