Its nothing new. So its still awesome.
Gameplay: The same as Doom - simple shooting! In Doom II they also introduced the greatest Doom weapon of all time - THE SUPER SHOTGUN. I'd use it over a plasma gun. Doom II's levels have more puzzle elements and the game is significantly harder as well. Thats not bad thing, though.
Graphics: Exactly the same as Doom - Quick, responsive, extremely playabke for today's standards and back in the day this was some of the best. Get Doomsday Engine to see even more beauty.
Sound: Doom II's soundtrack doesn't fail to disappoint, it is great. Doom II has new music so don't get worried you'll here the same tunes from ultimate doom.
The lovely sounds of hitting a Baron of Hell with a rocket launcher still remains.
Story: In the ending of Doom, you see a demon mothership on earth and everything's gone wrong. In Doom II, you solve this and kick more demon ass.
Value: Sometimes I wonder if Doom II should've been a DLC for the original bevcause it doesn't offer anything new apart from music, a weapon and levels.
Verdict: It gets a lower score because it is the same as Doom and it has been used already, but still. Doom II is really good. Buy it.
If you haven't played the Ultimate Doom, buy it off Steam now. What are you waiting for?