Rimworld.... a game you can play countless hours and in the end you will want to play it more. The setting of the game allows the community to just make so many mods and they come up with so many ideas, that you will be able to play this game for... well, forever basically.
"But hey, if this game only gets good by modding, isn't it bad then?"
No Timmy, definitely not. The game by itself is already great and allows you to spent countless hours in it, as it really is a Story Generator, how it calls itself, which always manages to throw something new at you, because there are so many variables in play, it'll be incredibly hard to just encounter very similar characters in the game, because there are so many factors in play. And if you then add mods on top of that, which change things up again or add things (I can really recommend the Vanilla Expanded mods for any newbies) then you really always stumble across new cool things.

11/10, would always play again