GR: In the '90s, there was much buzz about virtual reality and how it was the next big thing. But unless you count the Virtual Boy, nothing ever really came of it. I, of course, could see the appeal—imagine being so enveloped in a game, that your every movement, your every thought, makes it seem like you're really inside the game's world.
Motion controls took a minor step at bringing virtual to reality. 3D is another baby step. But at this past GDC, I was privy to an experience combining the two in an unusual way.