I just discovered this a few days ago. The Internet Archive (Archive.org) has over 2,500 MS-DOS games, which can all be downloaded or played in your browser, for free. Archive.org's MS-DOS Games Library - Over 2,500 Gameshttps://archive.org/...elibrary_msdos_games
Pretty much every DOS game I can remember playing as a child is there, only this time they're full versions instead of the shareware demos.
Combined with Archive.org's Internet Arcade
(a collection of MAME/Arcade games) and the Console Living Room
, you should be able to keep yourself occupied for quite some time.