Del Toro has an amazing aesthetic sense. His movies like Hellboy, Pan's Labyrinth and El Orfanato show this off beautifully. The same is true here.
Hellboy II's plot isn't the greatest: A crown, broken in three parts and distributed between humans and mythical races, when reassembled, wakens The Golden Army, which will destroy the world. Hellboy and his friends at the Bureau for Paranormal Research and Defense must stop the crown from being reassembled.
Most of the first half of the movie takes place in modern-day Manhattan, where members of the BPRD must remain cut off from the world and under close cover. However excursions from the mundane reveal creatures that are somehow awful and beautiful at the same time. This is del Toro's gift. He imagines creatures that are slender, graceful and muted alongside big, burly and bright. The canvas of his film is richly detailed - painting you can get lost in.
While I wouldn't recommend Hellboy II for the acting or story, it's a beautifully crafted fantasy picture. As long as del Toro keeps churning out films like these, I'll keep watching them.