Gaming

I have enjoyed caves of qud. Feels like every run is brand new.

Planescape: Torment is extremely replayable. I've been playing it every few years since I got a copy in I think like the early 2000s. It may be that this has something to do with having gotten to play it a little bit in the 90s but not having gotten to play the whole thing. There was a lot of anticipation there.

But I don't think it's just that. It's incredibly responsive to choice, and it's one of the first games I can recall with things like faction reputations and alignments. There's a lot there to dig through, and even once you have, it's always cool to wander around Sigil. It feels very alive.

The other one I end up replaying over and over is Shadowrun for SNES. That's not so much infinitely repayable though as just a really great game that I'm happy to run through.

Europa Universalis 4, Crusader Kings 2 and 3, Mount and Blade Bannerlord/Warband, Star Sector, Battle brothers, Path of Exile, Last Epoch, Grim Dawn, Stellaris.

Heroes of Might and Magic - the originals. Mostly 3, but any from 1 to 5 can do it.

6 and upwards, it's just pure Ubisoft enshitification. Can't even play them properly anymore due to the online component having shutdown its service.

Hades.

Shattered pixel dungeon

Risk of rain and risk of rain 2

Dead Cells! Made by a worker cooperative 🥳

The Binding of Isaac with all the DLCs. I really mean it. It's the most replayable game I ever played, not only that, but there's tons of mods on the Steam Workshop too.

I don't think any other roguelike comes close in just the sheer amount of things to do and see in this game. I've been playing on and off for years, have more than 500 hours and I still have challenges to complete, characters and items to unlock and item synergies to see.

I gotta get back into Ultrakill, I really wanted to start P-Ranking to get to the big boss fights.

Rally racing games; special stage rally is racing on a closed road and competitors start one at a time, competing for the fastest time at the end. These games are infinitely replayable in that you can always try for a faster time. The arguably best rally game is Richard Burns Rally, which has been kept alive by modding communities like the Rallysimfans.hu plugin, where independent developers continue to create new tracks and cars. Other fun rally games include Dirt Rally, Dirt Rally 2.0, Dakar 18, and BeamNG.drive (which has a massive modding community of its own) Special mention to the Gran Turismo series and Wreckfest, which both include rally among many other types of racing.

Rimworld would be my top suggestion, as others have noted.

I picked up Old World (excellent native Linux support BTW) during this summer sale and have not been able to put it down. If you're a fan of Civilization style strategy games I'd highly recommend checking it out. I haven't really enjoyed a Civ game since Civ 4, and Old World feels very similar but fresher and with less jank. it's got a Crusader Kings style dynasty system with randomized events that adds a layer of role playing your leader and securing their dynasty through heirs you can train/influence.

As for the repeatability, Old World has tons. Each culture plays significantly differently, and each leader has different bonuses that encourage an interesting style of play. Games don't play the same because of the mentioned event system, but also because learning new technologies is "randomized" as well. New techs are researched based off a selection of 4 drawn tech cards once you finish a previous technology. The card system makes it so you can't just rush straight to archers and dominate the early game to snowball into a power house every game, but its not truly random so you can "game" the system in your favor to get the techs you want with the tools the game gives you through either unique leader powers, or specific governor roles for example.

The game is super deep while not being off puttingly complex.

Kerbal Space Program, for sure. Skyrim is another.

Stellaris, Rimworld, the Sims, and a lot of stragedy games.

I think factorio is one, even when you launch your rocket (I have more than 100 hours and I don't think....) you still can restart in a new generated world and try do to it again in a better way.

My most played games outside of actually multiplayer games are arpgs. Diablo(mostly 2 and 3), path of exile, last epoch. Diablo2 and last epoch can be played offline, PoE can't. And yes, they're technically online multiplayer games but most people play them alone so they might as well be single player games to me. After that my most played games are RPGs and rogue likes. Plenty of good suggestions for that already

Many ppl suggest rougelike/lite and sandbox games I want to also add games with a good mod community and have a lot of side quest like Skyrim, they fit the replayability criteria because when it starts to feel the same can you add mods that change things up. I have done thousands of hours in Skyrim and never finished the main quest 😂 I think Balders gate 3 will also live for a long time. Many rpgs seem to get a lot of mods and games like Balders gate change a lot depending on what you do and how you play.

But you seem to want some kind of fps so warframe would be better, you can play alone or with friends. Just like ultrakill do you jump around killing, you can use, swords, guns and magic depending on your build (there are many). Doom would also fits your style of playing I think.

Otherwise management games is a time sinker. But most do not have fighting elements where you yourselves fight. Cult of the lamb tries to be all of it, it has action/fighting and management you can even decorate if you are into that. Pretty good for those who want it all. The devs still updates it too.

Sorry to be a soulsborne weeb but I have something like 1500 hours in bloodborne and I still pick it up from time to time

Anything with procedurally generated levels, like roguelikes/roguelites. I can personally vouch for the longevity of Slay the Spire, for one specific example.

Dyson Sphere Program is dangerously replayable to me. Hundreds and hundreds of hours sunk into it

Borderlands 2 has a lot of replay potential without getting boring. It never plays the same way twice. The weapon drops are very different each time through. Don’t forget the DLC. The rest of the games in the series are fun too, but BL2 seems to be where it peaked for me.

The binding of isaac: rebirth and dlcs

Kenshi is infinitely replayable, imo.

From the alternate starts, to the different ways you can even play the game (wanna be a lone trader, traveling from town to town buying and selling goods? Want to be the ultimate warrior who can go toe-to-toe with the Spider King? Wanna build a city/outpost where you can be totally sufficient and build up your own personal army to take over the world?), to the sheer size of the world. Plus all the awesome mods that can add so much to the game that already has a lot. You start off with your skills at 0 or in the low tens, and you will get your ass handed to you on an iron platter until you actually train up a bit; but even a high or max level character can still get fucked up by the wrong group of enemies.

I have mods that add a couple new factions (the fungoids are OP), flesh other factions out a bit more with more weapons and gear, and other building mods and some QoL mods so I can truly tailor my experience how I like it.

It plays kinda like an RTS with a mix of RPG elements.

Honesty I'm shocked nobody has mentioned Tales of Maj'Eyal or ToME for short. Extremely deep roguelike with story and it is getting expansions ans updates all the time.

Also it is open-source, so can be downloaded for free, but I would recommend you also buy it in steam for instance to support it.

Look up project brutality or brutal doom. Those are great doom mods with a lot of fun gameplay. I used to play that for hours.

The Anno series is pretty cool. It's like playing crack. I've been playing 1800 recently and it feels like an instant classic.

The elder scrolls games are great for this. The further back you go the more replayability there is IMO. Morrowind is goated.

Dungeon keeper 1&2 are both a lot of fun, and have lots of custom maps. The original dungeon keeper even has a full engine rewrite which is really good.

If you want to try map painters, Crusader Kings 3, EU4, and Victoria 3 are all excellent and in depth games, with a lot of replayability stemming from all of the different ways to build up your nation in the sandbox.

Rimworld, dwarf fortress, etc. Have fun!

Closest I can think of to infinitely replayable games are rougelike games like Slay the Spire, Peglin, Shotgun King: The Final Checkmate, Backpack Hero, etcetera, and sandbox games like minecraft (or Minetest if you don't feel like spending money and/or don't already have a minecraft account).

Though, with the rougelike games I mentioned, there are upper limits to increasing difficulty levels.

Classic Doom 1 and 2. There's gotta be over 100 levels if you count TNT and Plutonia, which I think were sold as Final Doom? Anyway, if you just get the base games for 1 and 2, there are thousands upon thousands of community made maps, including some total conversions, so you can play new Doom content until it physically pains you to continue.

Of course, I feel obligated to mention that even though it would be super easy to pirate the WAD files and play with a free modern source port like GZDoom, like absolutely trivial to find copies of DOOM.WAD and DOOM2.WAD floating around the net, probably showing up easily on Archive.org, but... Um... Where was I going with this? Oh, right, don't pirate. Cheap on GOG last I knew.

Strictly speaking about single player games, as in no rogue likes and such, Max Payne 2 is probably the game I played most times over the years.