Original graphic novels are also taking off big time, and manga as well. It’s the traditional periodical comic format that’s dying a slow death.
Comic shops stay in business by selling games, toys and tie-in merch as well.
It also depends on location, too, most of the failing comics stores I have seen are those in towns on the street side. In a given community, a fraction are going to be the comics fans that will buy the graphic novels, card games, etc., from you. A largely populated area will give you more, a large shopping mall is also a safer bet. But yeah, selling comics movies is what I see a lot of stores doing, at least those at the King of Prussia Mall, anyways.