Harry Potter is huge, but if you don’t like it or haven’t read the books, you’re probably not going to see the movies. I can guarantee that there were a lot of people who went to see the Avengers because it was written and directed by Joss Whedon - not because they cared so much about the Avengers.
You go, fellow Whedon devotees. You rock. Now it’s time for us to take over the world.