Replaying Heretic 2 back in 1998 with my first Voodoo (banshee) was a borderline otherwordly experience, compared to my first playthrough of the game using software rendering. Nothing has blown my mind the same way since.
I have had three experiences like this in my life:
1. PC Speaker -> Sound Blaster: Most games that I had were instantly upgraded
2. Doom: my first "real" fluid 3D experience, with stairs, etc, compared to maze-like maps in Wolfenstein
3. Software Rendering -> 3dfx (Canopus Pure3D): Transparent water surfaces in Quake (if you re-vis'd the maps), smooth and fluid visuals, it was amazing.
The closest thing to this, in modern gaming, has been the boss fights in Elden Ring: https://i.imgur.com/gzLvsLw.mp4 -- visually, they are quite epic.
