Actually, I came this close to mentioning this—a unifying setting or a world where each other places their game. I and others have brought up this idea before, a kind of nod toward the old Sanctuary fantasy books where different authors would set their story in the same city:
I could even see a mini-game that allows the player to explore the Main St. of this unifying world, and when they click on a link, it takes them to the individual game.