Although one usually makes a clear-cut distinction between games and simulators, I'll treat them as one on this subject.

  The best games for:

  Learning aerodynamics: Flight Simulator

  Learning WWII history: Hearts of Iron

  Learning Military Tactics: Panzer General

  Learning World History: Europa Universalis

  They are very educational, in a general sense. But not a replacement for a book on the respective subjects, of course.In my humble opinion.