Clapping after (or even during) a movie at the theatre isn't the same as clapping because you played a good video game or read a good book or whatever. When you do those things, you are alone.
When you are in a movie theatre, you aren't alone. There's a whole crowd of people, enjoying the same movie at the same time as you. You may not realize this, but this does create a sense of community. Everyone is enjoying the movie together. When everybody laughs together, this does add even more to the scene. If everyone enjoys a scene or the entire movie enough to clap, and they do it together, then it creates a great kind of experience.
I literally just got back from the movie and I am seriously not just pumped up because of how great it was, but also because of how fired up everybody else was about it.
If you are incapable of establishing this kind of connection with the people around you, then I feel sorry for you.
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The batman villians all seem to be one big joke that batman refuses to laugh at - SantaRPG