Doom II

The Good
(Assumes you're familiar with the original Doom)

I loved the double-barrel shotgun. That has to be the most badass weapon in deathmatches, because a direct hit with both barrels not only takes off 100% health from your opponent, but also has no travel time--it can't be dodged or avoided.

The new enemies are mostly improved versions of the originals with two notable exceptions. Running becomes your primary mode of transportation when the tall skeleton dude launches rockets at you that track your every move. And you haven't known fear until you realize that you're in the direct line of sight with something that can unleash BFG-like power on your ass with very little preperation time.

The Bad
Some levels and/or enemies are just rediculously impossible to beat. Thank goodness for quickload/quicksave...

The Bottom Line
If you liked Doom, you'll love Doom II. I guess that goes without saying, eh?