I think a large reason why people claim they are so hard is because, compared to the vast majority of games of today, they are significantly less forgiving. Although it's become a little less common, let's face it: most games today, if you die, you go back about 30 seconds and try again, and you can repeat this until you get through whatever part is holding you back.
Demon's Souls (and now the Dark Souls games) actually genuinely punish you for dying, something that many gamers who aren't familiar with really old school games probably didn't have too much experience with.
This is also why X-Com: Enemy Unknown had such a reputation for being hard: because the game actually made you hurt for losing, and in fact you could actually "lose" the entire game, even though honestly the game isn't that difficult once you get the hang of the combat and figure out the enemy AI.
Demon's Souls (and now the Dark Souls games) actually genuinely punish you for dying, something that many gamers who aren't familiar with really old school games probably didn't have too much experience with.
This is also why X-Com: Enemy Unknown had such a reputation for being hard: because the game actually made you hurt for losing, and in fact you could actually "lose" the entire game, even though honestly the game isn't that difficult once you get the hang of the combat and figure out the enemy AI.