The current game we have been playing is Borderlands for the X-Box 360. This game is a ton of fun. Picture a Halo version of Mad Max and the Thunderdome. This is what Borderlands is like.
It is a FPS, but has a lot of the same style of play as an RPG also. You are able to level up your character, collect guns, shields, and all kinds of ammo upgrades, etc.
They have also been doing a great job of releasing additional content for the game to keep it fresh and so you keep coming back to the game.
Overall I would recommend this game.