Here's a few things which make doom II better than more recent first-person-shooters:
- Not so many different keys to learn. Makes it easier for new people to learn (more deathmatch potential)
- Cooperative multi-player mode. Many newer games can't have this because the way they load in the maps.
- Doesn't require huge hard disk space.
- Doesn't require huge processing power.
- Can listen to mp3s while playing it.