For me it was the original Resident Evil on the Playstation.
It was the first time I saw live-action digitized full-motion video on a gaming system. I know there were a lot of FMV (Full Motion Video) games in that era on other systems, but I didn’t own those other systems and I didn’t know anybody who did. So, it was all new to me once I played a Playstation.
Resident Evil was also the first time a video game had ever given me a jump scare. Early in the game a zombie doberman bursts through a window unexpectedly and I was hooked! I loved introducing my friends to the game, specifically so I could see their reaction when the dog shows up. So much fun.
Honestly seeing and hearing Super Mario World on the Super Nintendo was kind of wow, too. The graphics boost compared to the 8-bit systems I was used to was incredible. And the sound quality compared to the other 16-bit systems I’d played (Genesis and TG-16) was a leap above. The experience probably pales in comparison to modern games, but back then there was wow factor to it.
To young me, Street Fighter 2 Turbo was pretty wow as well. It was “literally” the same as the arcade version to child me. I could not believe the home version was so close to the real thing, because prior generations of game systems like the NES couldn’t come close to that level of performance.