The well-known Internet „backup“, archive.org curated 2.400 classical games that can be played for free!
I am just listing some of my favourites games from the 90s here:

• The Ultimate DOOM (1995)
• Out Run (1986)
• Street Fighter 2 (1991)
• Block Out
• Unreal (1991)
• Bubble Bobble (1988)
• Hexen – Beyond Heretic (1995)
• DOOM 2D (1996)
• Giana Sisters (1987)
• Winter Games (1986)
• Heretic – Shadow of the Serpent Riders (1996)
• Bundesliga Manager Professional (1991)
• Microsoft Flight Simulator (1988)
• Eye of the Beholder III – Assault on Myth Drannor (1993)
• Transport Tycoon (1994)
• Indiana Jones and The Last Crusade (1989)
• Frogger (1983)
• Pac-Man (1983)
• Tetris (1986)
• Sid Meier’s Railroad Tycoon Deluxe (1993)
• Micro Machines (1994)
• Castles (1991)
• Duke Nukem 3D (1996)
• The Incredible Machine 2 (1994)
• SimCity (1989)
• 3D Lemmings Winterland (1995)
• Battle Chess (1988)
• Lemmings 2 – The Tribes (1993)
• Commander Keen 1 – Marooned on Mars (1990)

You can also find games for Apple Computer, Atari Computer or ZX Spectrum on their site.

So feel free to go back to the 80s and 90s. Have fun.