Mine is vehicle building games like Stormworks or Scrap Mechanic. It’s so much fun to shoot at your friends with your latest nuclear drone while hiding in your bunker with a better defence system than Area 51 !
I’m very curious about your fav niche game genre !
(I’m sorry for my bad English ^^')
I would recommend starting with Rimworld. It’s a lot like Drawf fortress but it replaces the insane depth of Dwarf fortress with more accessibility for the average gamer. Think of it as a more streamlined Dwarf fortress. If you feel like you need more depth then there’s always Dwarf fortress.