Ah man this really is tough, your post details a lot of what’s on my mind, but I think ultimately these three win out;
Minecraft - especially given the fact that we have access to the entire modding sphere, it’s just plain silly how much creativity has been poured into this, and the game is pure nostalgia for me. I could get lost in it for aeons.
Dwarf fortress - wins out to CDDA because I’m a strategy nerd. What has ended up killing me in the past with this game is how much time it takes, but on a deserted Island? Well, time isn’t an issue.
The last one is perhaps the most difficult, but assuming that I have access to a sufficiently high-end pc, I’d want KoboldAI (United) with all currently available local models downloaded. This is only borderline a “game”, but I am able to modify the software, and the possibilities are simply endless for creativity. It’d definitely ease up the loneliness a fair bit.
Planetary Annihilation, Warcraft 3 (at least pre-reforged if you can get a hold of an old copy), Unreal Tournament, Killing Floor, Battle for Middle Earth (1 & 2), OpenTTD, Simutrans, Settlers: Heritage of Kings, some of the older Wolfenstien games, Battle for Wesnoth, Warzone 2100, Teeworlds, Widelands