Based on the amount of hours I’ve put in: Factorio or Kerbal Space Program

Both share the sandbox theme where you can play around and try weird stuff in your own tempo. You define your own goals, instead of just going for a stock goal.

Tetris kind of has a long running title on this topic.

I dont even like tetris that much, but it has captured the attention of generation after generation.

It’s probably one of the only games you could open in almost any setting and have people wanting to play it.

Minesweeper and Solitaire.