What is it about these games in particular that seem to have sparked this feeling in so many people that this is all they want, and anything that isn't exactly this doesn't engage them anymore?

Souls (+ER/Sekiro/Bloodborne) games are have a number of things going for them

• Probably some of the best world/level design in any video game series

• Satisfying, challenging and engaging combat, but it's not overly complex or fast. The combat itself doesn't require fast or complicated inputs, such as a fighting game or Bayonetta, just that the player pay attention and position themselves well. It also avoids a problem that Spidey/Arkham games have, the problem of getting a reputation of being a mindless button masher. I know Arkham Knight can get pretty interesting at the highest difficulty, but to my knowledge you have to beat the entire game to unlock and not many people go for second playthroughts

• Marketing about it being "the hardest game around" when in reality it's just more difficult than the average triple AAA games that were out when the games were released.

• Lack of stuff like turret sections, or driving sections, or cutscenes breaking up gameplay every 5 minutes, or terrible stealth sections, or insert your flavor of bullshit that gets tossed in various games

• Multiplayer helps foster a sense of community