Doom 3 is a legend in itself. The game has set benchmarks for other games to follow up on in terms of game play, visuals and scariness. With a host of weapons at your disposal including ripper, chainsaw, plasma and shot gun, you make your way through a demon infested ship of the United Aerospace Corporation as an unknown marine.
Parts of the game require you to flash your torch in one hand and then keep it down and shoot the enemy with guns based on where you saw it last while the torch was up. Some of these kinds of levels are pure scare as enemies jump up on you round the corners and attack you as you just pick some ammo or entered a new passage.
Doom 3's greatness also lies in its classic boss battle at the end of the game. That fight alone is worth playing Doom 3. You know there is going to be a hell of a fight when there is a lot of ammo stocked up in the room before.
The story in Doom 3 is kind of non important and you get it mainly via audio logs and emails.
Till date, any game I play in first person shooter genre or a 3rd person shooter like dead space, I compare it to the master piece that this game is and wonder why ID software didn't follow up on the sequel. This is one of the best games you can ask for in horror first person shooter. Its revival of the DOOM genre.