You keep on forgetting that kids love the movie. When a children's product is popular enough, it can become huge. It's not like it's that popular among actual adults. They're just around because of their kids.
But in relation to other musicals/disney movies, it is dominating without being better, is what I'm saying.
On topic though, Is there a "Frozen" game? It seems odd that there would be a special console without a big game to go with it. It's like having a Ninja Turtles Xbox, or something.