Although, to be fair, we played Doom over an RS-232 cable - hauling a PC across the city every weekend was a testament to our love for the game :)
The campaign has a place in my heart too, even if it's not perfect. A lot of DOOM's level design was predicated on claustrophobic interiors, and when you go "outside" in many levels it feels like a glorified courtyard. From the very first level, Quake 2 pushes hard to create an illusion of environmental complexity that plays very distinct from Quake 1 or DOOM.
HL1 took both the engine and the genre further + continued the modding culture that brough Counter strike and other mods
(Note I know very well that Half life is not an ID software game, it only took the engine that was auper heavily modified / updated- but it my opinion this is the successor)