Hard to pick.

Starting my first own game system. Before that only gaming was done in "video arcades"

Silent Service - Limping back to base with 75000t sunk, no ammo and sub barely functional.

F-18 - First vector graphics flight sim I saw, that wasn't just wireframe. Mindblowing.

Civilization - First playthrough with a friend.

UFO - Enemy Unknown - Storming the first UFO. Although game was similar to Laser Squad, it was still revolutionary.

Wing Commander - First mission ever. Game was like anything before and really tickled my Battlestar Galactica itch.

Comman & Conquer - Had played Dune before, so it was not the first RTS, but really hit the nail on the head.

Team Fortress - My first online gaming experience.

GTA 3 - Playing the first time. My first open world experience. Have had a little pause in my gaming.

B17 - Mighty Eight - Just barely ditching on English soil with only one functional engine after a suicidal mission.

Alpha Centauri - First playthrough with the Mrs.

Battlefield 1942 - After Wolfenstain Enemy Territory, open space and vehicless felt amazing.

Elite Dangerous - First launch, first interstellar jump and first combat in the same flight. Elite games had been a bit boring on the sound and visual design before, but holy shit.

Deep Rock Galactic - Never approved any friend requests on steam before. Started approving them. Some legendary moment ensued.