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.
20th Century
Oregon Trail: https://archive.org/details/msdos_Oregon_Trail_The_1990
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
Sim Ants: https://archive.org/details/msdos_SimAnt_-_The_Electronic_Ant_Colony_1991
Sub Battle Simulator: https://archive.org/details/msdos_Sub_Battle_Simulator_1987
21st Century
Pox and the City: Edinburgh:
Places to find browser/based (no download) games:
http://poxandthecity.blogspot.com/
Lure of the Labyrinth: http://labyrinth.thinkport.org/www/
The Radix Endeavor: https://www.radixendeavor.org/
Darfur is Dying: http://mentalflosswww.gamesforchange.comorg/uk/games/26813/10-great-ms-dos-games-you-can-play-in-your-browsergame/darfur-is-dying/