Summary
A evil, cruel, demon-infested fun-fest!
The Good
Doom 2.
I can honestly admit that I played Doom 2 before playing Doom. With that piece of info out there, I love the game.
The graphics for its time are top-notch. In fact, compared to the games out know, I believe that they hold up their own. Sure, there are no belzier curves or multi-level playing fields, but Doom 2 had it all.
The controls are fantastic. Highly configurable, and really responsive, great for blasting a demon or two :)
The ambient sound is fantastic. Just enough demon-howls to chill your blood.
Level Construction is excellent. The desginers put a lot of thought into the constructions of the levels. Also, the option of playing through the levels with a 2-player cooperative mode (if hooked into a LAN) is a feature I wish that were included in the newer games (See Nintendo's Perfect Dark for a shining example of this).
Also, the amount of new maps available give this game UNLIMITED replayability. On a personal note, There are a few mods that recreate the WOLF3D levels that are worth checking out as well.
The Bad
There isn't a lot NOT to like. It's a fantastic game all around.
The Bottom Line
It's a great futuristic game with plenty of replayability. If you get it, I guarantee that it will sit on your hard drive. You won't want to delete it.