I dare say that games are preserved more through digital means then by physical media though. You have plenty of sites keeping different versions of a number of games, old or new, without any form of DRM (or bypassed) on PC (through "piracy", as ironic as it may sound).

Physical media nowadays are mostly a form of DRM anyway - a disc that will only work on a certain system, and that usually requires you to go online to activate it anyway, which means that they won't work after a couple of decades (or even much earlier). The biggest advantage of it, imo, is the freedom of selling/buying or trading used copies.