Asklemmy

For me: Easily Portal 2.

A deeply rich story, funny dialogue, and great puzzles that will truly make your brain think. The story is very rich and spans across several different eras of Aperture history, going as far back as the 50s. The dialogue is funny and some of the lines are the most memorable in all of gaming (like the Cave Johnson lemon rant). And last but not least, the puzzles are great. They start off pretty simple, but as you progress further in the story, they get more and more complicated, especially when you get the repulsion gel and proposion gel. I feel like Portal 2 is the Gold Standard for puzzle games that every game that comes after it will be judged on.

Also, if you don't own Portal 2 yet, now is a fantastic time to get it - it's on sale for $1 on Steam, same with Portal 1. And if you want both games, the bundle containing both games is $1.50. Do not miss out on this offer, it's so worth it.

I have been playing a lot of Arma reforger and rimworld lately and I love both but they definitely won't meet everyones taste.

factorio

the dedication of the dev is perceptible, almost unlimited replay value and the will release a major extension in 9 days that looks wonderful.

Cyberpunk 2077. I've been known to simp pretty hard for this game, but I do consider it to be one of the best games ever made. The story, the music, the acting, the gameplay, the visuals... Every single part of the game is just masterfully done. I feel it's one of those games that everybody should play; a sort of "milestone" game like Ocarina of Time or Skyrim. Even if you're not a fan of FPS or RPGs, it's worth turning down the difficulty and playing just to experience the best story ever told through a video game, in my opinion.

Outer Wilds.

If you like space games and puzzle games (in the sense that you need to piece together the situation you're in), this is a great choice.

Highly recommend not looking anything up before you play.

Subnautica

Stardew Valley.

Its revolver has continuously released huge updates for free and has commuted to never charging for dlc.

The games mechanics are pretty great and nothing in the game requires too much grinding to get.

Even when you “finish” the game, there are still things to do and starting a new files is always fun.

The characters are all great and have unique personalities. It really makes you feel like you are part of the town.

My wife and I have over 400 hours on a single file. It’s also enjoyable starting a new file. I like to challenge myself to see how quickly I can do certain objectives in the game.

It’s also decently cheap and has a huge community behind it.

None. Buying isn't owning and piracy isn't stealing. Pirate all the games!!

Drag really likes Deathloop.

Hades

Hollowknight my beloved

I'm currently addicted to Chained Echoes, a 2D SNES style rpg adventure.

Half life, all of them, in order

Chess

Absolute Balderdash. It's the most replayable and funniest board game with a crowd. I've hurt my ribs many times through laughing too much.

If I had my way every domicile in human history would have one of these and a pair of decks.

Kerbal Space Program

If you like good storytelling, worldbuilding, complex flawed characters and/or deep interactive internal monologues, Disco Elysium is unsurpassed.

Valheim

Katana Zero: Just try it. It's a 2D action platformer with good story.

Terraria

Metal gear solid 3 is IMO one of the best games ever made

Celeste. Great fun Mario-level game, but with a deeper story in both game and in development.

There could be hundreds that I post here, but going to just say the ones I go back to again and again.

Satisfactory, The Planet Crafter, Stardew Valley, Death Stranding, Kerbal Space Program, Cities Skyline, Cyberpunk 2077, Stray, Red Dead Redemption 1 & 2, Duke Nukem 3D, Doom 1 & 2, Decent, and of course Skyeim.

The classic Doom collection, classic Doom has a massive modding scene and you can put the wads into a source port like GZDoom.

What platform? I can think of multiple must buys, but it really depends on the system.