I've always loved Doom. It was my first FPS, and it blew me away. Constant, fast-paced action. Who cares it has a wafer thin plot? It's got brilliant, thrilling level design and monsters who come at you from every nook and cranny. It's got surprises but doesn't need a deep plot for this. It just needs for you to pick up a blue key and the walls to suddenly raise, an array of wonderfully, creepily snarling demons to attack and adrenaline and sometimes fear to overtake you. The thumping, ever-changing, mood-setting soundtrack adds to the game. You may be in a dark tunnel with heartbeat like music pushing you along, or in a full-on bloodbath with roaring rock music.
Then arrives Doom on Playstation. Same gameplay. Slightly different level design. However it technically equals the game in that department, although I'm still fonder of the original. It's only pitfall is the music. It's slightly techno and can be good when it gets going but can be too quiet to provide atmosphere. Sound is quite creepy, however, and equals that of the original PC edition. It also beats it in value - 2 games in one! Ha!
Overall, Doom is a masterpiece, whichever platform you play it on (Doom 64, totally different game though, that story may be told another day....)