Carmen Sandiego and other DOS games.
Apparently the state of online game emulation has advanced since I last thought to check. It looks like archive.org has a bunch of titles, including the original DOS version of Where In The World Is Carmen Sandiego?, playable right in the browser.
I played this on the Amiga, so the graphics and sound were way better (I think the Amiga itself was able to boot into DOS somehow), but it's definitely the game that had me eagerly poised over a world atlas in my early grades, memorizing locations, capital names, cultural promontories, and flags.
Part of me wonders what the legality is around this – you'd think the self-declared Internet Archive would do its homework. The other part remembers asking itself decades ago how many video games had ever been made, when the seeming answer already lay on the fifth order of magnitude. Video games will become literary in scope, with treasures buried beneath generations' worth of other treasures.