Hmmm now reading some of the comments here, Demon's Souls was NOT "impossibly hard" in the same way that some old school games were eg. Contra.
I like to describe it as more of a learning experience. Dying is part of the game. As in, the game would lose it's charm if you did not die so much...I'm serious. It's all about learning from YOUR mistakes. It's not cheap...when you die you cuss YOURSELF cuz it was your fault, not that the devs gave you some almost impossible situation to handle.
Ponder this...my first play-through took about 100hrs. My 3rd took about 4hrs. What does that say? By the 3rd time I was aware of all the game's tricks, and wasn't going to fall for them anymore.
It also isn't really a single-player game...it's online by default. The only way to play offline is to sign out of PSN. Players always leave messages on the ground warning of dangers ahead, and you can leave your own too. You can always summon a player from their game to your own to co-op an area if it's really too much for you. Or if you're feeling evil...invade someone's game and slay em for no reason.
And the combat...man oh man...just the best since like...Zelda. It's visceral and satisfying. The sound of metal cutting flesh is calming. Combined with the dark atmosphere...and you truly feel like a badass Demon Slayer. Anyone who loves the atmosphere of game's like Elder Scrolls, Dragon Age, Witcher etc is gonna love this.
Had to do this lil writeup cuz it seems people unfortunately avoided this game because they think it's the wrong sort of "hard" lol. I'm a casual gamer myself and trust me when I say I would not have Platinum'd this game if it was "impossibly hard" and "cheap".
It's one of the highest rated games for the PS3 for a reason folks...and it looks like it's still going strong.
Hopefully Dark Souls is of an even greater caliber...and you don't avoid it for the same reason =]