MarvinKitFox

NetHack is a magnificent work of art. A friend of mine in college introduced me to it a dozen years ago and it still keeps me entertained.

Dwarf Fortress is definitely an eternal work in progress, but, well, so is KSP. The interface is awkward but there's a lot of fascinating depths to explore once you get the hang of it. I haven't played it in a year or so, but I like it for a lot of the same reasons I like KSP--wide open sandbox world to explore, set goals to achieve with available parts, put a lot of thought into carefully planning something in great detail and watch as the plan becomes glorious success or hilarious failure.