Let me preface this by saying that we are all just stating our personal preferences, so please don't take any of this as a hint towards Anno's future!
Personally, I have always had a sweet spot for ancient history- Greek, Roman, but also Persian (being Half-Iranian myself), starting with some child-appropriate books when I was pretty young (“Was ist Was”, for the Germans among you), and I am always happy to see these cultures reflected in games, of which there are thankfully many great ones. In fact, Age of Empires was the first game I ever bought when I got my first PC!
The other historic culture I have a soft spot for are Vikings, which are also quite popular in entertainment these days. Come to think of it, I think my employer recently released an excellent Viking-themed game 😉
Best,
Marcel