Check out this interview on CTV.
...Now all A-movies are B-movies. If you get bitten by a radioactive spider (Spider-Man), that's a B-movie. If aliens invade the earth (War of the Worlds), that's a B-movie. Tom Cruise can jump up on Oprah's couch all day long, but it's still a B-movie. If you dress up like a bat and fire on Gotham City (Batman Begins), that's a B-movie.
