Absolute favorite is Outer Wilds. The only thing I don't like about it is that I can't experience it again. A true masterpiece of a game.

After that, probably Noita for sheer insanity. Deeply unfair, but getting a god-run going is that much sweeter. It took me ~100 hours to beat it the first time, now I can consistently win if I try but I'm addicted to doing stupid things to see what happens.

Synthetik is my top steam game with, like, 900 hours.

Super Daryl Deluxe

That game has one of the best soundtracks I've ever heard in a game.

Just looking though some of my higher playtime games, here's a few I haven't seen mentioned: (I think they're all indie or small studio)

Gunfire Reborn - Roguelike fps with infinite replay.

Troubleshooter Abandoned Children - XCOM style battle system with a really really fun way to customize how your character fight. Story is pretty lame though (I ended up skipping it) and it's pretty grindy.

Thronefall - Pretty challenging base defence.

The last spell - Turn based base defence with lots of different ways to build your characters.

Ratropolis - Roguelike real-time card strategy base defence. Pretty good, although not well balanced at highest difficulties.

Sticking only to ones I haven't seen mentioned:

• Tandis : geometry puzzler
• Gateways : a 2d portal-style puzzler
• Elliot Quest : pixel adventure
• Phoenotopia Awakening : also a pixel adventure, had trouble with the final boss but the rest is great
• Wuppo : flash-animation-style comedy adventure
• Alba : sweet game about a girl who loves wildlife
• Salt and Sanctuary : 2d soulslike
• Legend of Grimrock : tile-based first person dungeon crawler ("dungeon master" spiritual successor)
• A Short Hike (really short but amazing exploration game)

Ones I have seen mentioned but can't bear not to mention:

• TIS-100 : the finest of the Zachlikes; a programming puzzle game
• Crosscode : 2d adventure with incredibly fine-tuned combat and puzzles
• Outer Wilds : fantastic time-loop puzzle
• FTL : space adventure "one more run!" game
• Slay the Spire : deck-drafting "one more run!" game

Rimworld

I suppose I've plugged it recently, but Another Crab's Treasure.

It opens pretty plainly as an ocean-based Soulslike parody with a simple story premise and some self-subverting humor in the dialog with other crabs. As you go on though, every 20th conversation becomes really pointed and real-world-connecting, going beyond just "pollution bad". It's not quite Spec Ops: The Line, but it at least has something to say about society.

The combat is frustrating but addictive, much like Souls games - and it's okay with handing off a number of allowances like accessibility modes and tip systems. It's even helpful that, if I die to a glitch or something bogus, I can actually just choose to re-obtain my microplastics (souls) through a menu.

Celeste is one of my favorite games period, and it qualifies. The gameplay parallels the story better than any other game I've ever played or seen played, and the soundtrack, art, and characters are amazing. Top tier gameplay and a great story to go with it.

Alternatively, if you're looking for absolutely unhinged strange gameplay made by a programmer rather than a game designer, check out Fractal Block World. It's pretty fascinating!

For me it's Rimworld

Minecraft (the old one)

Tactical Breach Wizards

Currently it’s Bellwright, among many other titles. what particularly tickles me about it is the shitty ai voices they used for the npcs. I am not pro ai by any means, but nothing makes me happier than hearing “all in a good days of work.” delivered constantly, in the most off-kilter reading imaginable.

Factorio, hands down

600 hours and counting. The space age expansion basically quadrupled the content, and is the first time I've played the game 100% vanilla with no mods in probably 10 years. Great times.

Minimetro and Cultist Simulator are my go to "comfy" games, but cultist simulator really does get you feeling like you're chasing a mad eldritch horror when playing at times. It's deliberately obtuse and odd, and then a revelation of the truth takes you over and you push on beyond your wildest expectations.

Slay the Spire and Hollowknight have both been mentioned enough in other posts in case anyone reading this is somehow unaware of either of them.

Faster than Light and Into the Breach are both excellent games. FtL is rng mitigation and crisis control par excellence. ItB is basically chess, and you play out the turns as best you can. It's rewarding, but once you get good you need to ramp up the difficulty somewhat to keep it fun.

Probably Indiana Jones and the Great Circle. All the older Indy games weren’t that great but this new one is really good.