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.
Funny you say that. Mario Kart DS was peak offline social gaming for me. Back when it came out, lots of kids at my high school carried their DS on them and lunch was nothing but Mario Kart. At least it was among marching band nerds. And if someone happened to have a DS but not Mario Kart, we'd just do Download Play so they can at least join us in a limited capacity.
Ahh... I also wanted to live that... But I was the only dude that had a DS in my classroom... Heck, I dare to say all classrooms of my age lol.