Quake II. Certainly one of the FPS that really began to popularize multiplayer, Alongside with a kick-ass campaign, and a blasting soundtrack that is still superior to this day. And guess what. Its engine gave us Half-life.
I purchased the original Quake 2 when it came out, but it has become stale over the years. It's nice to see an updated and refreshed version plus the addition of the "Call of the machine" expansion. The inclusion of preproduction artwork is ok, nothing to write home about. It was quake II 64 that that was really fun. I suggest buying it when it goes on sale. Definitely worth it.
This is my first time playing through Quake II and I'm pretty impressed, mostly by how many tropes I associated with Valve were actually pioneered by id, particularly the near-seamlessly connected maps, weird spinning technological set pieces, environmental puzzles, poorly maintained Industrial treatment facilities, and funnily enough, rotating valves. You can really see the similarities in Valve's GoldSrc engine.
The enemy AI is reactive at times, often ducking and retreating. Though the bigger, tankier enemies get easily stuck on corners, which is pretty exploitable. The weapons all feel satisfying and each serves a purpose. The compass is absolutely crucial and a clutch addition to this modern update. I really wish the same could somehow be done for Doom 1&2 to replace the overhead map. I don't know what navigating this game was like before this update, but being able to load up my save and immediately get my bearings straight is such a good quality of life feature, especially in older FPS games which can seem labyrinthine.