1) Continuity - Doom 1, and Doom 2 came in a relatively short sequence, and were then followed by the Quake series (which was pretty much the same, let's admit it). Much easier to remember a series that affected a whole generation.
2) Doom (or at least Doom 2) had successful multiplayer. I spent most of my freshmen year in the old computer lab playing Doom 2 deathmatches against dorm-mates.
Wolf 3D was a fun game, but it wasn't really memorable as a franchise. The gameplay wasn't as good as some earlier in-the-nazi-castle 2D games, and the sequels were not particularly successful and came many years later. There were also a lot of copycats that were pretty much the same principle but different tiles.
I remember downloading the demo for doom and having my mind blown. Doom was the first major shooter to give a sense of verticality, even though if I'm not mistaken the map design really didn't let a player be at different heights at the same time.