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.
There are some very memorable games.
No game has ever matched the freedom of Morrowind. You are only limited by yourself. Even Oblivion and Skyrim feel restricted by the game itself.
Half-Life 2 interacting with the environment. I must have played with the can for hours the first time.
Final Fantasy VIII though was the single most impressive game for the hardware it came out on. The character models being actual human proportion, the summons looking like actual monsters, and the FMVs where people look like damn people in a movie.
In the same vein, FFX being described as looking like FFVIII’s FMVs but all the time. And then living up to the hype.
Morrowind mentioned, based comment.