Minecraft, specifically Beta 1.7.3.

Monkey Island or Little Big Adventure

Learning Team Fortress 2 for the first time as a teenager was such a crazy fun experience.

Half-Life 2 and Shining in the Darkness.

Portal 2 and Undertale the true pacifist run

Homeworld

FF6, FF9 and Links Awakening

Morrowind but it wouldn't matter because I don't have enough time to get immersed in it anymore.

I know this is almost a stereotypical answer, but the Witcher 3. because after that game i went and read through all the books. so if i got to re experience it would be the difference of finding siri after 100 hours of gameplay and finding siri after 5000 hours of story. "find siri' is Geralt's primary motivation throughout the books. i can only imagine how satisfying and emotional that scene would feel for the first time with the weight of the books behind it.

Space Invaders

Asteroids

Pitfall

Read dead redemption 1. A masterpiece.

Quake 3 Arena. Or more specifically OpenArena + baseq3 and other mods like ratmod. Most fun I have had playing a game ever.

Bioshock. I am sure you can just replay it. The twist at the end... I wish I could relive the surprise again.

Probably Fallout New Vegas (if that even counts as retro yet). I've played it to death ever since it came out and can't even remember the first time I completed it.

That'd have to be Metroid: Zero Mission and The Legend of Zelda: Wind Waker. Two of some of the only games I actually 100%.

Hotel Dusk.

Wings for Amiga, flying in WW1 and a cool story between missions. Everything I know about ww1 air battles, I know from that game :)

That Zelda is on my list for sure. I'd add super Mario world as well, just like Zelda did, it introduced so many new mechanics and the maps were so HUGE you could spend absolute weeks trying to unlock all of certain areas.

NBA Jam on SNES.

Wolfenstein or Doom first time really seeing a 3d game. Being absolutely terrified of the ambient noises in Doom.

Half-Life for sure. Relatively intelligent soldier opponent tactics, puzzling real puzzles in 3d for the first time not just point and shoot.

Goldeneye 007. Trying to figure out how to aim, so slowly and ineptly. Then one of your friends says let's try multiplayer and 4 years later...

Warcraft 2 on dial-up with your friend across town.

GTA 2. Discovered almost by accident and the top down view was so great. Never cared much for the rest of the series.

Super Bomberman.

Ghost Trick: Phantom Detective

The story has so many great twists and turns even up to the very end. There was a distinct point about 75% of the way through when I came to the realization that I had to binge the rest of game. Even if it meant I got zero sleep that night, I had to see how it ended.

It was so good I wish I could experience it again blind.