Literature is basically defined as a story being told in a way that absorbs its reader and transports them to another place in time and immerses them into a new world. Since graphic novels tell a story that can essential do this, just with pictures and words, yes it counts as literature.
Graphic novels tell a story, however deep that may be. It could be as riveting and deep as Pride and Prejudice or it could be as silly as the Hitchhiker's guide to the galaxy. I read both graphic novels and books, and they provide the same storytelling experience, just in different ways.