Hmmm. Hellboy 2. What can I say? More of the same? Maybe not. I think the characters seemed more developed, the story was good with interesting characters, monsters, and villains, and it was written and directed by Guillermo del Toro (Pan's Labyrinth).
So overall I'd have to say that this sequel bucks the trend (that most sequels suck) and was actually a decent continuation of the first film. I had fun watching it and I thought the visual effects were top shelf!
So if you are a Hellboy fan, or a "We made a movie out of this comic book" genre lover, then by all means, wake the baby and check out Hellboy II.