Minecraft (the old one)

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.

I really liked What Remains of Edith Finch.

It was more of an experience and really struck some emotional chords, leaving me write emotional at the end.

Really beautiful and melancholy experience.

Anything of Soldak - https://store.steampowered.com/franchise/soldak/ : 2 series - space shooters Drox and hack n slash Dins - Super coarse graphics, action, fighting, but their living worlds, like nowhere else. No other game where worlds freely grow based on player actions. Did You ever left main quest for exploration, lvling up or side games, oh well, here, world will not allow You to, as enemies won't stay idle or wait for You, they do their business.

Orb of Creation - https://store.steampowered.com/app/1910680/Orb_of_Creation/ Semi-clicker (intense clicker, not much of idle) and immersive mage simulator, where You don't make Your mage-avatar, but are the mage. Still beta, but already big.

For me it's Rimworld

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

Monster sanctuary (turn based monster collector) and Roboquest (arena shooter) were a couple from recent years that stood out to me

For older games nethack and dwarf fortress are great if you can look past the graphics

Tactical Breach Wizards

Live for Speed

I've been playing it on and off for over 20 years now with some definite highs and lows but I have nothing but respect for the devs (3 people) and community. It's not on any store fronts and they just do their own thing.

LINK

Most of what I play is indie and choosing a favorite is too hard, so instead I'll go with biggest playtime. Antimatter Dimensions, also on Steam, has quickly shot to having the highest playtime of my Steam library. It is an idle/incremental game. Bonus points: free! Most of the idle/!incremental_games@incremental.social I have played have been free in the browser without IAPs, and seem to have been made by one or a few people.

Not counting that, I'd probably have to go with Stardew Valley.

Top of my list right now is Vintage Story! It's like a serious version of Minecraft, with more focus on realism.

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.

Stardew Valley

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

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.