It did improve a ton on the Wolfenstein formula.
Wolfenstein 3D was a game where pretty much everything was broken down into squares. Corners were always 90 degrees. Doom allowed for variable size walls (linedefs in the old DEU), rooftops, etc.
It added the third dimension, actually incorporating differing heights into the engine. The level design was lightyears ahead of Wolfenstein 3D. Not to mention the graphics alone were way better.
Environmental Damage
A Variety of weapon effects (Wolf3D didn't actually have this.....the submachine gun was just a faster firing pistol, and the chaingun just fired two bullets at once, to simulate its higher rate of fire). This includes different ammunition types.
Multiplayer. It supported IPX and serial connections so that people could deathmatch. We can all thank Doom for engraining the term "frag" for when we kill people in a deathmatch game. (Don't confuse this with online play, which was first supported in Quake).
Lightmaps. The game actually featured variable lighting.
A dynamic environment....it was possible for triggers to actually change the environment.
Just looking at the two, I wouldn't be too surprised which one actually turned people's heads.