The reasons why I like the first one are because it was dark, serious, and the humor was at the right moments. As for this one, it had way too much humor, it wasn't dark or as much serious like the first one, and it had moments that make you say, "Eh, it's alright." Though the action scenes weren't that bad, they were really great, and the plot was rather interesting and very original, the concept designs of the creatures were amazing, and the special effects were really fantastic. The development of the characters were explored much more. But I hate when some actors don't return, like Agent Myers played by Rupert Evans in the first movie didn't return. I understand that he was busy with some other movie at the moment, but at least give him a short cameo or something. Let's just hope he returns in a third one, if they decide to make another one.
As for the story, the villain Prince Nuada, who was played by Luke Goss from Blade II, had a great motive and certainly is a original character. His motives were very clear. The fact that he's tired of the human race, and wants to take over the world by rising the robotic, mechanized, unstoppable force of the 'Golden Army'. I like that this movie is original and not basing off from anything, except the characters from Hellboy of course. Johann Krauss, which the voice was played by the famous Seth MacFanlane who created and voiced in Family Guy and American Dad, was indeed a good introduction to the series. He was interesting, smart, and funny at the same time. He kind of reminds me of Stewie Griffin from Family Guy, without the whole "I want to destroy my family and the world one day." I like the subplot that Prince Nuada and his sister Princess Nuala have this kind of connection, whereas if you beat up Nuada or kill him, his sister feels the pain and dies the same as well. Very interesting. Sad for Abe (Doug Jones), he loved Nuala and now she's gone. Kind of makes you want to cry, huh? Also the relationship with each of the characters (Abe and Hellboy, Hellboy and Liz, Abe and Princess Nuala, Hellboy and Tom Manning, etc.) were very realistic and natural.
Overall, good movie, not the greatest sequel, but a very original idea by Del Toro himself and Mr. Mignola. Like Spider-Man 3, you can watch it over and over again 'cause it's really fun to watch over and over again. Here's hoping for a Hellboy 3.