[Jach]

Nintendo is an interesting case, because while the stores are gone/going away (though there was a Wii->Wii U transfer period), a lot of the games themselves aren't gone, and what you already downloaded will continue to work so long as you don't delete it. More importantly Nintendo itself is still around (and will probably be in another 20 years -- there are many long-lived entertainment companies) it's just that they (and others who re-release on the new stores) want you to keep re-buying the same games over and over.

I have a similar desire to paxys in that I want to be able to play most of my games in 20 years, where such a concept is even valid (I do sometimes enjoy multiplayer games and other things "of the moment" where I have no expectations of playing the same game tomorrow due to a sweeping patch or upgrade or shutting down, let alone in 20 years). It's just that digital store risk, especially of Steam, is the least of my worries.