VGA Planets is the most complex strategic diplomatic game ever. Got my personal copy from Tim personally in the early 90's.

Is a originally for 11 players, round based, very long lasting game. 500 Planets, 11 different races wit different advantages and disadvantages.  You can play it now in the web browser on some hosts as https://planets.nu and others or create your own host an play with (or against) your friends. This time there are also a lot of addons to the original rules. And if you like to play, you should not be too lazy to read all the documentations, hostorder and experience reports. Have fun. I played it many years also in german championships.