Sega was up first, demoing that version of Super Monkey Ball they've been working on. The real key on this one will be the amount of content they can come up with, and the devs have said they're planning to put in lots of levels -- the more the better. It will debut for $9.99 right at launch.
Pangea was up next, showing off a few ports they've put together -- Cro-Mag Rally is a "caveman racing game" that uses the accelerometer (surprise) to drive a vehicle. This is, unfortunately, the problem you run into when you get a really innovative set of controls on a gaming device. It takes innovation not only to come up with the controls, but to find new ways to use them. Just as the Nintendo Wii suffers from thousands of useless minigame collections, the iPhone at App Store launch will likely suffer from thousands of "accelerometer racing" games, with only one or two really worth playing.
But Apple saved the best for last -- a company named Digital Legends was invited to show off their action/adventure platforming game, and it showed real promise (you can see some good screenshots on Engadget's liveblog). Unfortunately, this one won't be out until "a few weeks" after the App Store launch, but hopefully for every touch jewel puzzler and accelerometer racing game we have on release day, we'll have a truly innovative gaming delight later in the iPhone's lifetime.