As far as I can tell, the Lego genre was invented by fan filmmakers, not professionals. I can't prove that, mind you; it's just that the idea to act out a movie with Lego toys seems more likely to emerge from a suburban basement than from a Hollywood studio. But the big boys are jumping on the bandwagon, to judge from what appears to be an officially sanctioned professional production, Spider-Man: The Peril of Doc Ock.
It's an impressive film, both on a technical level (the stop-motion photography would do Ray Harryhausen proud) and as an entertainment (though it's closer in spirit to Airplane! than to a superhero movie). You can watch it here.