Would run and gun games count? If so, I strongly recommend the Neo Geo Metal Slug games. They're all sold emulated on PC (GOG for the no launcher requirement).
And on a more usual sense of "shooter games", Saints Row The Third (GOG and Humble Bundle) and UNLOVED (original version is a mod of Doom II afaik). And just a note, Saints Rows The Third, from some tests I did a while back, seems to have a memory leak issue in character customization screens when running under default Wine.
And some times, having the initiative to create such more specific communities could be a change factor for the growth of a social media. Also, with federation, not just the person can choose where to create the community on while not making it a walled garden as other sites would still have access to it, but also if a community for the given subject already exists but the user thinks he can do better, he/she can more easily do it with how expansive the "fediverse" is.
Growth is a process, not an immediate switch. Every social media started small and then grew. If immediatism, or however it is called, was the predominant factor for any struggle to become an achievement, nothing would be achieved.
And on lack of contents, I, for one, block everything that is not of my interest, quite a lot to be honest, specially with certain niches spamming the federated platforms, but even then, I get a feeling I should trim even some of the communities/magazines I follow/subscribe to as I can barely catch up to those already.
Instead of "good guys", feels more like "drunk guys". They removed the games from everywhere, and even the moderators from GOG's forum, despite usually trying to be as silent as possible for any matters (specially thorny ones), seemed at loss when that happened. And now, out of the blue, EGS granted permission to use Internet Archive's uploads for the games.
Though I have yet to get a Deck for myself, I'd probably use it a lot to read comics. Having used the Vita a lot for that, being able to control the comics with a physical controller was fantastic, and the far greater processing power of the Deck should also avoid pages taking a long while to load (loading Humble Bundle's ebooks in measly 512 MB of RAM is an experience).
Regarding the question itself, Starbound and Minecraft. Maybe Final Fantasy XII if I was to play it multiple times, as I take at the very least 100+ hours to finished it, and 250+ if I'm not in a hurry.
But regarding gaming fatigue, perhaps it could be a symptom of playing too much of only a handful of game styles? If you wouldn't mind, may I suggest to check some smaller games in length and scope, specially indies? Those tend to be rather diverse in their scopes and executions.
While I think fragmentation can grow into being a problem, trying to standardize things too much can be problematic too, as the developers would be bloating the software for features that the community may use very little, as well as, by consequence of the bloating, the devs being either limited to a design that needs to take into account the quirks of all object formats, or to make some frankenstein monster design to include those different formats.
A more reliable path, I think, is what Kbin (RIP) and its successor Mbin do, to have a section for articles and one for notes. While it's still more load on the developers and the servers, at least it shouldn't be as much as having to make sense of multiple formats together, since the two sections don't directly interfere with each other. This, on a final point, is, to my understanding, and with their respective proportions, what happens with the Linux family of operating systems, where it's also pretty fragmented, but every once in a while a way to put two different environments together appear, like Wine and Xfce translating Windows and QT5 programs, or AppImage and Flatpak trying to be as universal as possible by depending on as little default dependencies from the host system as possible.
Something I've been thinking about is that changes only happen organically, so I think it's good to not be an insistent advocate for a platform X, Y or Z. Instead, I think that perhaps it's better, instead, to simply use the platform the person is more favorable towards whenever possible, and if people then share something worth sharing, it should slowly bring people over. And regarding the annoying part, at most, making a note about technicalities and the type of people in the site could be good if discussions the person is engaged in allows, and if the person didn't burn people's patience by being pedantic.
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.
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).
Would run and gun games count? If so, I strongly recommend the Neo Geo Metal Slug games. They're all sold emulated on PC (GOG for the no launcher requirement).
And on a more usual sense of "shooter games", Saints Row The Third (GOG and Humble Bundle) and UNLOVED (original version is a mod of Doom II afaik). And just a note, Saints Rows The Third, from some tests I did a while back, seems to have a memory leak issue in character customization screens when running under default Wine.