I saw this film with my husband on the weekend...poor guy gets dragged to lots of films he wouldn't normally see. Suffice it to say he really didn't like it at all. He's never read the comics and has only been exposed to Del Toro's wonderful visions of the character so he didn't 'get it', particularly the one-liners and it's gruesome nature.
In contrast, I have been a fan of Mignola's comics and Hellboy since the early 90's and frankly this film is the first honest use of the source material. In particular I loved Babayaga and the hellions that showed up near the end of the film, but the whole thing was like revisiting my best Hellboy comic moments.
My opinion on why so many critics have been piling on with the negative reviews: Though I never expect everyone to agree or like any particular property, many critics have little understanding of what Mignola's work is about and can't move past Del Toro's version. It's not snobbery to expect that stories be told as close to their original source but it is lazy (and possibly snobbery) to not do your homework.
Good work, folks. Bring on more!