I still think it's Wii Sports Resort. It's a game for everyone, plus it's soon to be released in Japan, so they need to show it to the people. Unluckily, I think that Zelda will be revealed at next E3 for a 2010 holiday launch date.
They will never use a 3rd party game to showcase new tech. So it won't be Red Steel 2.
Proud poster of the 10000th reply at the Official Smash Bros Update Thread.
tag - "I wouldn't trust gamespot, even if it was a live comparison."
Bets with Conegamer:
Pandora's Tower will have an opening week of less than 37k in Japan. (Won!)
Pandora's Tower will sell less than 100k lifetime in Japan.
Stakes: 1 week of avatar control for each one.