I really like Isle Wars and Scorched Earth

Gotta go with Dwarf Fortress. Been playing on and off for the past 10 years at least, it's just endless !!FUN!!

Rimworld

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!

Most of my picks have been mentioned already, but I had a blast with Mullet Madjack. A tongue in cheek riff on 80s anime in a boomer shooter where you have 10 seconds to live, but each enemy kill gives you 2 more seconds of life.

Some I really appreciate that I'm not seeing on this list:

I'm currently enjoying Blue Prince which is a fairly new rogue-like puzzle/mystery game it's hard to explain without spoiling but it's worth looking up.

Portals of Phereon is one of my absolute favorites. It's a fairly deep tactical RPG thing with loads of replayability. It's kind of like a Pokemon x FF Tactics but with monstergirls and it's also currently free while it's in development. Be aware it's extremely NSFW and horny, which I suspect is the main reason it's not as popular as some of the others listed (IE rimworld, stardew valley, etc.) however the horny is such a key point to it's original gameplay and world-building that it wouldn't be the same without it.

Thea: the awakening is a decent tactical RPG. I love it for it's original battle mini game, crafting system and world-building. It unfortunately has some balance issues and jankiness that prevents it from being an all time favorite, but it's definitely one I would encourage at least trying.

Thought of a few others:

• Reus (2nd one's alright, first one's excellent)
• Library of Runia
• Book of Hours
• Kenshi (saw it listed one other time, but it deserves a lot more love)

I haven’t seen it mentioned and feel like it should count, since it really just had a solo programmer working with a graphic designer and musician, but RollerCoaster Tycoon and RollerCoaster Tycoon 2 took a big chunk of my gaming time.

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.

I remember playing an RPG back in the day called “Dink Smallwood” on my old Macintosh laptop, it was one of the few games that were Mac compatible. Really funny and self aware dialogue, pretty great! I found out there’s an app version of it for mobile

Clonk Endevour is not my favorite game, but I played it a lot with friends when I was younger. You can play with 2 or even more people, with just a monitor and a keyboard! Also it's so old it should run on any potato.

edit: real answer is Slay The Spire

edit2: ah shit now all of a sudden all the good indie games I played pop up in my head. Project Kat I enjoyed. Synthetik was awesome. Caves of Qud hasn't been mentioned yet (didn't play it much though).

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.

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.

Can't believe none of these haven't been mentioned yet: Starsector Kenshi Graveyard keeper Battle brothers Ghost of a tale

Gunpoint. Charming, atmospheric, doesn't outstay its welcome.

hypnospace outlaw

Undertale

Can't really add much to all of the great games already mentioned. But I'll add one, because it was one of the best games I played in recent memory. Chants of Sennaar. Where to even start? Point-and-click adventure/puzzle game that is all about language puzzles. With great visuals and music. Really dig the eurocomics inspired style. I don't know why, but this game really touched me - maybe it's because the game is about uniting people in an age of discord.

Magicraft.

Super Daryl Deluxe

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

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

NaissancE

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.

Clair Obscur: Expedition 33. If that doesn't count. Will....HoloCure or Noita or Parking Garage Rally Circuit.