As usual for declined "gamers", almost the entire thread is filled with "cool details" that are exclusively graphics whoring and fluff. And OMG, did we mention games used to have MIRRORZ? All the graphics whoring decline you begged and screamed for is why games can't have mirrors anymore, to prevent rendering extremely complex things twice.
Here's some random cool details you may not know, 90s edition, which I chose to give these games their due respect - features or accomplishments rarely spoke of in gaming circles when that should not be the case:
Ultima Underworld (1992 - PC) - Striking walls with melee weapons (e.g from a miss) damaged the weapon's durability. Game had a lot of cool little details for 1992.
Duke Nukem 3D (1996 - PC) - Some pretty incredible dynamic AI on display, such as an enemy type that would engage in ground combat normally like any other, chase, shoot, open doors and all that stuff, but also dynamically activate a jetpack and leave the ground any time, and for example fly up to you while blasting away, and land again where you are. He could also teleport. Killing him as he teleported resulted in him coming out the other side bleeding out, or even instantly gib. Hail to the King of FPS. One of them anyway.
Turok (1997 - N64) - Game had amazing platforming mechanics for a first person game, such as a brief grace period to still perform a jump after running off a ledge, as well as consistent speeds whether in air or on the ground, and lastly almost instantaneous stop speed/minimal inertia. All the things that (typically) make for great platforming gameplay, and if you're lucky you'll get just one of these in other first person games. Not that all FP games should have this, but many would have seen benefit.
Final Fantasy 7 (1997 - PSX) - a game so large and ambitious it had an entire modest-sized interactive theme park built into it as a mostly optional side distraction, as well as sub-games encompassing many major and minor game genres including FPS, Arcade Racing (x2), Snowboarding, RTS, Beat em Up and more. Said it before, will gladly say it again.
Vigilante 8 (1998 - PSX) - A vehicular combat game where almost every static mesh could be destroyed. Knock down trees, blow up buildings, rail guards can be destroyed in individual segments, and even the base ground geometry could be distorted and dented. All of this factored into the gameplay in a meaningful way. Very close to fully destructible 3D environments on PSX in '98. Even if in primitive form, it's more than 99.9% of games. Total overlooked classic.