Steve Dave Part Deux said:The "rebirth" video was meant to show off the GC's ability to stream video. And the metroid demo didn't even look as good as the final game. Besides, unlike PS2, they're aren't many developers pouring their heart and soul into pushing the visual envelope on GC. I'm not saying that the image quality of the demos wasn't higher than most GC titles but it certainly wasn't BS. If you're looking for BS try the old "Project Reality" demos.
Just want to mention that part of the Rebirth demo was realtime.