I find it incredible that Doom 3 was so highly reviewed when it came out. I get its supposed to be slower paced and more scary, but this game is not really that fun to play. As I said, static graphics, environments and lighting all look really good, they must have looked incredible at the time. But the character models and demons look really wonky. Imps run all crazily, and when you kill them the ragdoll physics are laughable. THe cacodemons have physics like baloons, When you shoot them they blow and tumble all over the place.
But really its just the boredom of the game. Its - go into a tight room, hallways, industrial type area. Shine your light around, kill demons who are hiding/pop out. Turn around as a monster closet opened behind you, kill, oh some demons spawned kill. Then explore area, go to next corridor/area. I just finished the hell area, that actually got different and a bit cooler, but now im back in industrial areas again.