Doing this fast so these aren't actually in a proper order, just 10 games that I think make my list, all for varying reasons.
1: Fallout 2
2: Space Station 13
3: Dwarf Fortress
4: Metro 2033
5: Victoria II
6: The Binding of Isaac
7: Project Zomboid
8: Sunless Sea
9: Dark Souls
10: Stardew Valley