There's a difference between "Scary" and "Dark", but I don't think ID know about this.
Doom 3 isn't scary, it's just very predictable. Oh look, the lights have gone out... Oh look, I bet a monster will be here... Oh look, it looks gorgeous...
Admittedly I've only played for a short time, but so far Doom hasn't exactly seemed like it is more than a game demo. Maybe it picks up as you get further in.