Going by some notes I have, for example, the Japanese versions of the Castlevania games, and also the games in the Namco Museum Archives collections.
Auster
Sadly some ROMs are only distributed through Steam, and others, at least until the next month, in reference to the ones Sega is delisting, can only be reasonably obtained there.
But indeed, Steam is not trustworthy, in this proposed case due to a publisher being able to simply disable a game's depots instead of mass revoking licenses. And while I understand the points on getting physical medias, to my understanding, digital medias could work as an ownership system, but it would require a given platform to both distribute stuff DRM-free, and to understand that the copies an user gets are his/her to keep. (but on a side note, back up everything you can, including receipts, ASAP, just in case either the dev/publisher or the store pull a fast one).
Is fighting between people supposed to be funny?
From the little I have seen, there seemed to be quite a few on Misskey instances, though I don't know how representative it is if compared to, e.g., X/Twitter, where most of the artists I would find were at.
Maybe set up the VM yourself, then make a shortcut on the desktop and say to your friend to just open it to play the game? Also not very familiar with Windows, but maybe you can set up a script on the VM to open the game at the system's startup, and to automatically turn off the system when the game closes?
I don't know how much of a subset I am, but I still use dictionary softwares from Windows 95~2000 era and Android softwares on a completely offline and vanilla VM, partly due to internet randomly going bad, and partly because I am neurotic about digital contents vanishing once support ends.
Can it be used offline?
I think we misinterpreted each other.
In my original comment, I mentioned two separated cases. First, a "some ROMs", referencing a more general landscape, and then the Genesis/MD collection from Sega specifically. And the "reasonably obtained" part is because some editions are very hard to come by, may be very expensive, and/or may be a nightmare to have the ROMs extracted from.
Then, with your reply, I thought you were asking about the former, when, going by my following reply, it would seem you were asking about the latter and that you thought I was talking about the latter too.
Would that be the case?