Well, when you really get down to it, there's not much in Demon's Souls that makes it more of an RPG than Zelda, aside from its wider variety of weapons, armor, and spells.
I kinda classify them in their own genre, alongside games like Okami. Third person action games all about going on an adventure, revolving around the exploration of a rich, detailed, and open world, action-based combat, and some light stat usage. Shadow of the Colossus would also somewhat fit in here, though it lacks in item variety and stats compared to these others.
I can't think of a specific term for this genre, however. Third Person Adventure, maybe, but that implies something akin to the old PC adventure games of the 90s. Honestly, just straight up Adventure would fit perfect, but its already been taken. =/
Whatever you want to call this genre, it's my favorite. And such games are markedly different from most JRPGs and WRPGs, like Lost Odyssey, Fire Emblem, Whight Knight Chronicles, Oblivion, and the Witcher.
I haven't played much of Fable, but I think it would come close to this genre as well, though it has elements putting it a bit more in the WRPG camp, I believe, as well as in the sim camp with Fable III.