I recently booted up Half-Life 2 to replay it. I have played the absolute shit out of this game before, so 60% of it just feels like a drag to me now. It was such an amazing game but it's sort of spoiled for me after I've played it too much.
I also discovered ULTRAKILL a few months ago. I feel like I could play that game forever. It has tons of content, weapon combinations and higher difficulties with different enemy behaviour.
Do any of you have more game suggestions like Ultrakill? A really replayable singleplayer game.
!!BTW I don't mean online multiplayer games or games similar to candy crush!!
Definitely was my first thought. I think that I've spent way more time on that game than I'd like to admit.
Even if one gets bored of the game itself, there's a practically infinite number of mods and community content out there. New game modes like skyblock, mods that turn it into an RPG with magic systems, mods that make it an in-depth factory building game, mods that take you to new realms and thousands of items to discover... There's a lot to enjoy.
Adventure maps are also fairly underrated. There are tons of community-made maps that can turn it into a different game. Notably, there was a huge Hogwarts campaign with quests and spells that turns it into a harry potter game: https://www.youtube.com/watch?v=BKcsoE5X4fc
Obligatory Rimworld shout out.
I've dumped more hours into this game than the rest of my game library combined.
Edit: typo
A significant number of comments have mentioned Rimworld, guess I'll install it. Thanks for your recommendations!
Dwarf Fortress, if you like rimworld but prefer gigantic learning curves
My son and I had a blast with this one. We took turns doing runs through all biomes and found tons of blueprints and secrets. So fun!
Minecraft, Hoplite, Shattered Pixel Dungeon. You probably want a good roguelike.
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.
Basically any game that doesn't in itself follow a story, so you are the story (or make it). For me personally it's building and factory games, like Factorio, cities skylines (1 or 2), satisfactory, Kerbal Space program (1 only), Rim world.
This list is essentially endless.
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.
Fallout NV is fucking amazing, holds a really special place in my heart. Skyrim's great too.
Generally games with random elements are considered to be good for dumping tons of hours into. So games with randomly generated worlds like Minecraft, roguelikes, strategy games that are always variant just because of the nature of AI actions always being a little randomized, and other stuff like that. So maybe like Minecraft, Dwarf Fortress, Crusader Kings 2 or 3 as like a basic list. But really the game that's going to be the most replayable is the one you don't get tired of. I've beaten Thief: The Dark Project hundreds of times and that game is a relatively simple level-based stealth game with no random elements and not even especially huge levels.
War for the Overworld (I have many thousands of hours in this)
Settlers 2 Gold
(Both the above have a lot of user generated maps, which has given them most of their longevity.)
Factorio
The binding of Isaac.
I've been playing it on and of since the flash game released 13 years ago.
