Civ V: Brave New World for me, though it's just DLC. The new gameplay concepts are interesting and I can't wait to try them out. But that's out next week, so for the longer term, it will be Legend of Zelda: A Link Between Worlds. That is the game that convinced me to finally get a 3DS when it comes out. A Link to the Past was the first Zelda game I played (it came with my SNES) and introduced me to the series. A direct sequel to that game should be pretty good.