Internet Archive preserves old video games, including PC MS-DOS games. The latest update allows players to play around 2500 retro PC MS-DOS games, including all-time classic like DOOM, The Oregon Trail, Wolfestein 3D, Leisure Suit Larry and many others. Since this uses EM-DOSBOX, Emulation isn't perfect for a few titles, but most are in a good, playable state.
Archive.org: Software Library: MS-DOS Games (playable for free in browser)
Archive.org: Software Library: MS-DOS Games (playable for free in browser)
Software Library: MS-DOS Games