Physical media really doesn't help, because many games are delivered with bad bugs. These are fixed by updates. Unless you can actually download and archive the updates, reinstalling a deleted/corrupted game from backup media alone is impossible.

What is needed is a consumer bill of rights that requires companies to provide the purchased game with the latest update to the buyer upon request should they abandon it. If the game requires a server, that software code should be made public domain. An abandoned online game's copyright should also be voided. That would allow the gaming community to legally provide updates and servers for continued use.