X series - most complicated spacesims in existence (nothing realistic though)
Stellaris
Imperium Galactica 1 - a super-complicated 4x space DOS game - think Stellaris + SimCity + Command & Conquer
An obscure unpopular old game - Battle Isle: the Andosia War - or as one reviewer roughly said: "they must have had a board where everyone who came up with an idea got a golden piggie - it would work as 3 games: Battle Isle, Economy Isle, and Energypipe Isle, but this is just too much". Basically a turn-based but real-time strategy game (unit movement is turn-based, you can end your turn at any time but... resource extraction is real-time and if you run out of energy and water simultaneously you can't cool your power plant and you can't power your pumps). Also maintaining a supply-line behind your advancing army.
ernest