Except, you can't play traditional games on the iPhone. No dpad and no buttons severely restricts what types of game are possible.
I'm as much as fan of the iPhone as anyone, but let's not get carried away here.
What can't you play? I have racing games, 3D platformers, flight simulators, shooters, RTS, and puzzle games on mine right now. I'll admit Bugdom 2 is kind of hard to control but it's completely playable and it could be better if maybe they made a touch screen D-pad instead of using accelerometer controls.