As I was preping the post about Resurrection of Evil for the Xbox this morning, I noted two similar screen shots that show the big differences between the Xbox and PC versions of the game.
Here you will find Xbox on the left and PC on the right.
Basically, these shots really show off the texture differences, which is to be expected as the Xbox simply isn't powerful enough to run Doom 3 with high quaility textures. The lighting, however, is beautifully done in both versions, showing off the power of the custom nVIDIA card that was created for the Xbox (I don't know the specs of the PC used for this shot, but I would expect it to be using a high end nVIDIA card from mid-2004).
These shots are also significant in showing how, even though not as pretty as it's PC counter-part, the Xbox version is still great looking, and it's a testament to the strength of the big black box that it can even run a game like Doom 3 in low-res, something the other consoles could not do.