FPS games were built differently than they are now. They used to be survival mazes. In the 90's some FPS games were the stand-outs of that decade, like Doom, Quake, Half-Life, and Unreal. What's your favorite 90's FPS? The only ones I've played so far is Doom and Doom 2, and I use the ZDoom source port. Alsop be sure to tell the source port that you used (if any) along with that game!
Goldeneye 007 was a good one. Doing missions while being sneaky, blowing up stuff and trying to do it as fast as possible. Games in general are not the same as they were in the 90s, though. But Goldeneye is probably the only FPS I've ever played. I don't really play them in the first place. They're all the same, I feel.
I'm a big fan of FPS games from the 90s. The ones I play the most are Doom and Doom II, using the GZDoom source port for single player and Zandronum for multiplayer, although nowadays I almost always play Doom with the Project Brutality mod (a mod of a mod for Doom called Brutal Doom). Other 90s FPS games I've played are Wolfenstein 3D and first three Quake games, which I highly recommend along with Doom and Doom II. The source ports I used are DirectQ for Quake, Yamagi Quake II for Quake II and ioquake3 for Quake III Arena and Team Arena.
Although I still play quite a few modern FPS games and enjoy them, I do miss the "survival maze" level design style of 90s FPS games. I find it more fun to play and more interesting to explore than the linear style with cutscenes that many shooters have adopted nowadays, such as Call of Duty.
I am amazed nobody has mentioned the original Starsiege: Tribes (or Tribes 1, if you prefer). One of the most groundbreaking games of its time since it added the whole dynamic of "skiing" and pseudo-aerial combat.
Another game we played quite a bit was the first Team Fortress which was great for multiplayer LAN parties (back when LAN parties were a thing..)
Before Tribes I remember we played a lot of Doom and Wolfenstein 3D. Some other notable favorites were (as already mentioned) Golden Eye 007 for the N64 (remember those?) and Quake for its modding capabilities (from which our fabled QuArK map creator is derived from).
Some of the underrated gems from the 90s were the Star Wars: Dark Forces series (both the first and second) were very cool and at the prime of the Star Wars hype bubble. They even used the same engine to create a really cool wild-west shooter called
(come on, isn't that the coolest game you've ever seen?)