[rvba]

The true successor of ID software is Half-life 1 with its goldsrc engine... but that simply was made by another studio.

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)

[bombcar]

I always felt Serious Sam was the real spiritual successor of the original Doom lineage.

[skeeter2020]

Maybe they're related by blood, but the apple fell very far from the tree. the ID guys were quite vocal in their dislike of the slow pace & puzzle solving. This was when ID was all about technical advancements and repeatedly making the same game, faster & shinier. They also focused on multiplayer with Quake III arena and Unreal Tournament dictating where the market moved.

[StilesCrisis]

Don't forget that the entire Call of Duty series also sits on Quake's shoulders.

[AtNightWeCode]

goldsrc is based off the q1 engine.