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.
My buddies and I had easy access to a theater, which had giant curved walls on each side of the stage. We hooked up three projectors to three Xboxes; One projector for the stage, and one for each of the curved walls. Then we ran them into the sound system.
We did it two or three times a week for months.
The funny part is that you could always tell who was screenlooking, because the screens were so big that you had to physically turn your head away from your own screen. And at that point you just die, cuz you start missing the people right in front of you.