Very little of it lasts for long. And if it does, it's legacy banking or some ossified terrible thing people are afraid to touch - not something revered.
Every piece of software today will be rewritten. By 2100 much of it will be dead and gone. Like punch cards that have rotted away.
Or there's this 87% number, but it's based on "no longer a legal way to buy it," not that it's not archived/preserved: https://gamehistory.org/87percent/
We don't have to count amateur projects but the commercial releases in the US is not the entirety of the gaming history. There are other countries with their own rich gaming histories and other platforms (e.g. browser, mobile) that don't get the same attention as American releases for PC or popular consoles.
I cannot play a single game from my childhood, they were early flash games "for girls" and they were not in English. Nobody archived those.