I rate Hellboy 1/1.
Hellboy himself is an excellent character. Funny without being wisecracking. No angst like Spider-Man, not a big blue Boy Scout like Superman. Smokes cigars. Likes cats. Punches holes in walls. The supporting cast is pretty good too - the character which stood out most in my mind is the first guy the FBI agent meets at the BPRD. He only appears once and has about three lines but I liked him. Maybe I'm crazy.
Scenery was nice. CGI was good but not outstanding, particularly as far as the pyrokinetic's blue fire was concerned. Final bad guy wasn't particularly impressive: just tentacles, really. Characters were imaginative, dialogue was good. Storyline felt as if it was missing some background clarification - or maybe somebody who'd already read the comic books, which are highly spoken-of.
Do not see it if you dislike walking corpses.