I would say these certainly could be done real time with next gen hardware, the camera angles limit the draw depth in the street shots for one limiting the geometry seen at any one time, plus if you added a little fogging (make that smogging) you can reduce draw in effect as you move through the area, instead of abrubt draw in you can see things emerge low res gradually through haze until they're sporting full texture right next to them. Not to mention point of view depth of field being used. It certainly doesn't have the feel of the vast world that i saw in the Unreal3 demo. I guess it all depends on what sort of ambiance you want, character driven or environment driven.