Carmack has already said that there will be other games with higher poly count models at its time of release. Most of the polygons in Doom 3 will be taken up rendering the shadows. Think about it, if you have a single square (2 polys) floating in space, it becomes a 6 sided cube (12 polys) when it casts a shadow (5/6 cubes sides being the shadow, the other being the square that you actually see). The complexity increases even more if the shadow is cast on something other than a flat surface.
With Doom 3, raw polycount on the models and maps has been sacrificed for doing the realtime lighting. This makes the static screenshots look bad, but watching it in motion is really cool. The Doom3 engine isn't about pretty screenshots, but making scenes move realistically. The realtime lighting, combined with the bump mapping that is everywhere in the game will make it look really cool to play. And as far as I know the engine can do colored lighting, one of the screenshots clearly shows it.