Quake 1 was an unbelievable tech breakthrough: full 3d, quakec vm, overall engine design held up really well. It was not a perfect game but it was ok.

I still hack on the engine and its derivations from time to time.

Quake 2 was a development of that, will a deep focus on multiplayer. And it won at that. As a singlr player game it was boring but LAN play was just amazing.

So quake 3 did rethink the engine but went all in on multiplayer.

As funny as it may sound but in the end, it is quake 1 that just keeps going thanks to its easy moddabilty.