@daneian: This is probably the biggest thing for me. Overall, I think the gameplay mechanics are better, along with the character progression/upgrades, but the world itself isn't as interesting.
Much prettier, absolutely, but so many areas have an entry and an exit, with nothing else. In DS1, each area felt like it had multiple ways of entering and exiting, with shortcuts that would interconnect with other areas that you wouldn't expect, making it feel overall like a much more cohesive world. DS2 feels much more point-to-point style progression, which is kinda strange.
Weirdly, I think I still prefer DS2 overall.