Below are examples of games that, to one extent or another, are educational. Some were simply entertainment products created and sold by game development companies. Other games were developed by private developers, educational consortia, teams in higher education, and so on, for an explicitly educational purpose. All those below can be played in your web browser; you need not perform a download and installation process.
Life & Death 2: the Brain: https://archive.org/details/msdos_Life_and_Death_2_-_The_Brain_1990
Where in the World is Carmen San Diego? https://archive.org/details/msdos_Where_in_the_World_is_Carmen_Sandiego_1985
Sub Battle Simulator: https://archive.org/details/msdos_Sub_Battle_Simulator_1987
Pox and the City: Edinburgh: http://poxandthecity.blogspot.com/
Lure of the Labyrinth: http://labyrinth.thinkport.org/www/
The Radix Endeavor: https://www.radixendeavor.org/
Darfur is Dying: http://www.darfurisdying.com/