Every genre has its diehard fanbase: those who play that type of game almost exclusively, who dissect and discuss that type of game endlessly, who extract perfect routes and methods, and who analyze their systems to pinpoint what defines them. Some fanbases are inundated with games of their chosen genre; a pile of games to sift through, rigorously test the game’s mettle against their own standards, and decide whether or not to dig into them or, more likely, toss them aside and move on to the next.
I see it on my Steam friends list, those RTS fans who are constantly playing the new offering, or those survival fans who give every Early Access entry a fair shake. However, if one were to step back and examine their timeline of play, they’d notice these gaps between new games - but these ‘gaps’ aren’t downtime, they are just all the same game, the one they return to endlessly. They are the One True Game of that person’s favorite genre. They are Crusader Kings 2, or Don’t Starve, or Civilization 5.
I think what we see with games like Bloodborne is that they represent a genre whose fanbase is as hungry as any other, but are sorely underfed. There just aren’t that many fully-realized entries into the Souls genre. As with other fanbases, there are favorites of the genre, the One True Game that best represents it and offers the most depth, complexity, and replayability; however, unlike other genres, there isn’t much to test against this fanbase’s high standards, let alone those that are good enough to meet them.
I think that’s why large swaths of people tend to all gravitate to the same ‘old’ games from time to time: in between major releases of their favorite genre, these are the games which still have meat on the bone.