All files work with any doom game be it DOOM shareware,registered,Final DOOM,Ultimate DOOM,or DOOM 2
Doom Legacy
This is the best.I recomend that everyone get this.It adds full 3d to the game.You can look up,down,even jump.It even supports high resolutions.GET IT.
gldoom
Yep thats right,a program that makes DOOM accept 3d acceleration.It doesn't add anything real to the game,but it does make it look so much better.This will bring back some fun into DOOM.
The Simpsons Wad
What would any list of Doom files be without this classic.It changes the enemies in Doom to Simpsons characters,and you into Homer.It is a very well done wad.No Doom collection is complete without it.
ZdooM
This is basically Doom Legacy only done a little better.I would get this over Legacy ,but they are both great game files.