I remember a few from various stages of my life (born 1984).
Seeing the demo footage of Sonic 2 in Woolworths and thinking the leaves falling down in Aquatic Ruin zone was so cool and advanced.
The original Sega arcade of Virtua Racing with the moving cars completely blew me away.
I remember my uncle loading up Cannon Fodder on his Amiga, and a REAL song with REAL music came out, along with REAL photos. I was amazed haha.
A few years on I remember a PlayStation demo disc having promo footage of the first Gran Turismo and it looked so real to me, I watched it over and over. The first Driver on PS1 looked absolutely amazing to me also.
Star Control 2 on the 3DO.
It was my first CD console (never got into PC gaming back then), so while I had games like Donkey Kong Country and Sonic & Knuckles, the 3DO could do things that the 16-bit consoles just couldn’t.
The opening cutscene…voiced. The graphics blew my mind wide open, and the virtually fully-voiced adventure sucked me in for a long time.