Below is a list of several games that have similar mechanics, settings or that inspired us to create Civ13.
Rimworld - Similiar in the survival aspect of Nomads, you control a group of people starting from nothing in a planet.
Dwarf Fortress - A very complex roguelike. Features a lot of building.
Cataclysm DDA - A post-apocalyptic survival roguelike, with a complex crafting system.
Civilization series - Lends us the name, a 4X focused on expanding your civilization.
SS13 - The base code for this game.
Unreal World - A survival game set in the stone age.
Empire Earth - A RTS that is set in 15 different ages, from the prehistory to the future.