Personally, I try to collect the software for the machines that I'm interested. I've a fairly well-stocked collection of Amiga, C64, and PC software. I don't have to collect everything, of course, but for games/utilities that I like, I try to have original/complete copies. Once I have them, I produce bit-for-bit images as best as I can, scan the box/media/incidentals, then upload to preservation-minded torrent sites. Strictly legal? No... but as has already been said, the software and the hardware is essentially dead, and if the rights are held by any current companies, with few exceptions, they're certainly not mindful of the historical value of their IP. Like it or not, just as with preserving old film and written works, sometimes one has to step outside of the bounds of what is strictly legal and concentrate on the true value of what they're doing.
FWIW, I am currently trying to collect the complete DOS versions... so far, I've got about half. Given the prices of the remaining versions, it'll take a small miracle to find them for the prices that I want to pay (as most of us aren't lucky to have people donate to our madness - laugh!)