A woman on my Alan Parsons e-mail list asked if anyone had heard of "Video Games Live." According to her, this is supposed to be a "groundbreaking live event celebrating the music of video games," and that it has a full orchestra and choir, synchronized video, lighting, special effects, "crowd interactivity" and "live action."
Apparently, someone has already recorded (professionally) part of "Video Games Live," which happens to be on Youtube:
Another person on the list also mentioned several other videos on Youtube made by Guillaume Reymond, who did stop-motion movies of "live" video games. Below is "The Original Human TETRIS Performance," which is quite cute: