You want the most realistic lighting possible, but machines are slow and only have so much computational power, so what you do is you bake the lighting in advance. The way Gears of War looks so amazing is that most of the lighting is rendered ahead of time. It's baked onto the surfaces, which is awesome if the lighting stays in the same places and nothing moves, but when the light or something in the environment changes, it breaks it.
The next generation wants to get over that trade-off by doing the lighting simulation last after all the physical objects are in place. Not only do you need to add the lighting last, it needs to be a better lighting than it was when we pre-baked it. Zoner found a way of doing it. On Xbox 360 and PS3, we get about 90% of the way there. It obviously looks a lot better when you're playing it on PC, but it turns out the consoles are powerful enough, and all the software's optimal enough because we're so late in the life cycle, to where he found a way and we're fucking doing it.
It's pretty exciting for us. When you hear some of the big guys talk about their next generation lighting, you're going to hear about
deferred rendering a lot. It's very possible that Aliens: Colonial Marines is the first commercial product to ship with deferred lighting.