The only reason Demon's and Dark Souls are considered difficult is for its design and the way the game expect you to play it with not much guidance. Anyone that has put hours on both games will tell you that they are not hard, if anything they are pretty tricky, annoying and extremely enjoyable experiences. And after that a bunch people will say that you're crazy for even saying such a thing. But hey, it's true.
PvP is full of BS on both games though.
If people love difficult games, why aren't the ones I listed more popular?
people suck at playing video games.
I'm not saying that gamers are super humans, but to finish and play games like Ninja Gaiden Black, Vanquish or DoDonPachi Dai-Ou-Jou at their maximun levels of difficulty (like they are suppose to be played in the first place) is something that required a lot of passion and time. Something that not much people is willing to do.