Microsoft released three groundbreaking titles exclusively for the Xbox 360 this fall: the sci-fi fighter Halo 3, the philosophical horror adventure Bioshock, and possibly the best of the three, the new Mass Effect. This galactic game begins with humanity's frighteningly rapid colonization of space, and suddenly you’re rushing headlong into asteroid fields. The video-game basics are all there — you can blow stuff up and hop from universe to universe — but the real rush is found in diplomacy and decision-making. In this game, battles matter, but the fate of the galaxy also hangs on careful words and smart choices.