I really enjoyed the Dante's Inferno demo, the combat system was solid, I absolutely loved the setting and think it'll be no slouch in the hack n slash genre. It's hard to get any idea of depth from a demo, but my one worry was it didn't seem like the whole RPG elements / unlocking moves for Dante's was much to get excited about, albeit I guess that can keep the game balanced.
Saying that, I've not played the Bayonetta demo yet (It's on my hard drive waiting for installation lol), I've never played a God of War game (Release that GOW Collection in EU Sony!) and I'm pretty sold on Darksiders, minus the terrible choice of release date. Dante's definitely surprised me, but in recent years the only game of this type I played was Ninja Gaiden Sigma so maybe I just don't know better yet :P.