Those games have taught me so much about history and geography. On a game map you have to fill in every bit of territory with whatever state was there at the time, not just ignore it the way the history you're taught in school can.
It seems as though all educational games are created with a primary goal of "education" and a secondary goal of "fun game". The result is always an unfun game. What if the ordering were reversed? Create a fun game, then try to tack on some educational elements after the fact.
Perhaps some games like this already exist. I'm sure you could make a claim that Minecraft is a fun game that also teaches resource management and spatial awareness.