[owyn]

My guess would be Zork and the other Infocom games which at the time were huge because they could be played on the very limited PC's of the 80's and were top 10 selling games. Myst is basically a graphical "text style" adventure that was huge in the 90's and drove lots of CD-ROM sales and was a top seller for like a decade.

[macintux]

Aha, I misattributed the noun to which “these” applied. Thanks.