I think my expectations of Hellboy threw off my enjoyment of it. It's a good movie, shot well, suspenseful, doo dah doo dah, but I just didn't get any big tingle out of it (save for Selma Blair's eyes - wowsers). The critical raves mystify me.
The plot is the Nazis (always somewhat of a movie-spoiler for me, the sheer evil they represent is always a little too potent for fiction for me) try to awaken the "7 gods of chaos" and, though they are thwarted, a little demon boy slips through. He's raised by the American government, and is essentially a slave of the government, trotted out to help them deal with paranormal and especially nasty villains. The bad guys prove to be hard to kill, and thus come back from the dead to try and complete the summoning of the 7 gods in the present day. Joining Hellboy in hero/slavery are "Abe Sapien" - essentially the creature from the black lagoon reconfigured as a gentle, learned soul who can pick up psychic residue from things (ala Stephen King's The Dead Zone), and is voiced by Niles Crane (David Hyde Pierce) - and Liz Sherman - Stephen King's Firestarter all grown up, but, unable to control her talent, often sets off a minor atomic explosions of flame. Luckily her beau, Hellboy, is fireproof.
Ron Pearlman (of the old TV show "Beauty and the Beast" where he played a lion-like monster in love with the Terminator terror Linda Hamilton) is Hellboy. He does a decent job of emoting through the makeup (the extent of said makeup is unguessable as Rob kinda really looks like Hellboy, horns notwithstanding), but outside of some verbal zingers and a love of cats, he's not as well-drawn as, say, Spiderman or Daredevil are in their recent celluloid turns.
I still recommend it. About everything director Guillermo del Toro does has something in it to justify a viewing. I expect bigger and better things from him in the future, though. Heck, maybe even the next Hellboy will have some more meat to it.