My biggest gripe with the game was the fucking hitboxes and the fact that, although the game had a lot of variety, did so at the expense of immersion. I mean, a lot of areas were too "small". I felt that way. I would have preferred less areas but more fleshed out. That and the fact that the game didn't feel so connected as DKS1, but that is a common complaint. It's still a great game, better than most, but ultimately felt short compared to the previous 2.
Demon Souls feels like a hybrid between both Dark Souls games. It had good variety, and although the world wasn't connected, each big area retained it's own particular atmosphere. It was like 5 sub-games, but each of them big enough to sustain the momentum. DKS 2 had a lot of amazing looking areas, and inspired art design, but the areas were too small. One moment you're underground, the next you take a elevator to a dragon shrine. One moment you're on a pier fighting pirates, the next you're thrown into France. If felt very disjointed, albeit having a lot of very artistically inspired locations. I think it lacked "soul", no pun intended.
Dark Souls II felt a bit like eating sushi. Little portions, but so many different dishes to try out.