i've never had religious education at school or anywhere else, but i'm quite certain that he isn't a proven historical figure, he might have existed, but he certaintly didn't do all those cool magical things that fanatics say he did.
i really like how doom3 looks, the lighting, textures and models all suit the atmosphere of how the game should be, i think that the same graphics in half life wouldn't work, but they are very effective and look amazing in doom3