The movie looks great. Ron Perlman has Hellboy down, and the rest of the cast is fine, too, though I did kind of miss David Hyde-Pierce as the voice of Abe Sapien.
The plot is your basic ring-of-power tale. A crown is divided into three parts that, if reunited, will give the wearer power over the Golden Army, which can destroy the world. So our paranormal heroes have to get the crown. Complications: Hellboy and Liz are having domestic difficulties, and Abe Sapien falls in love. This results in a lovely duet by Hellboy and Abe on "Can't Smile without You." Barry Manilow would be proud. Other complications: the human world isn't as fond of Hellboy and his pals as it should be, so will they go over to the dark side? Maybe because I've never read the comics, I didn't get some of the backstory stuff about Johann Krauss, and his seemingly sudden change of character threw me at one point.
Lots of fights, lots of explosions, and the screen is crammed with wonders. I didn't think it was a masterpiece, as a lot of people seem to, and it went on a little too long. While it's clearly a much better film than Journey to the Center of the Earth 3-D in just about every way, I had a lot more pure fun watching that one.
Oh, and if you're wondering why I didn't go to Mama Mia! it's because the theater was (I'm not making this up) sold out.