Two years ago this month, as editors worldwide were beginning to debate whether anyone would actually go see Avatar, the $200 million-plus, 3-D movie extravaganza that James Cameron was making, Josh Quittner wrote in Time about getting an advance look. “I couldn’t tell what was real and what was animated,” he gushed. “The following morning, I had the peculiar sensation of wanting to return there, as if Pandora were real.”

It was not the first time someone found an entertainment experience to be weirdly immersive. For all the cutting-edge technology that went into the making of Avatar, in that...