It is starting with games, games are a great fit, and the games are going to be awesome. But it will become huge through immersive sports, immersive music, and most importantly, immersive storytelling.
Why? Because regardless of technology by far the most popular entertainments are ones that people can enjoy passively. Many more people regularly watch sports than play sports. Many more people enjoy music performances than play music. Many more people read books, watch TV, and go to the movies than play video games.