The iPhone doesn't have the necessary hardware to support proper gaming, the touchscreen is nice and all but as far as I know it has no haptics support (yeah the whole phone vibrating when pressing anywhere on the screen doesn't count either).
It needs buttons, plain and simple, not even Nintendo, the kings of alternate controls schemes, have managed to get rid of buttons in their Wii and DS consoles.
It's not going to be a true portable console gaming platform in my opinion, it's just going to have some good games but that's it, cell phones have some games but I wouldn't consider them a serious gaming platform.
That being said I don't think Force Unleashed will be a good game, heck, when you have big budget you just release the game on every thing with a processor, Warrior Within was available for my old Nokia 6103 (a crappy phone) and I don't see anyone calling that phone a true portable console gaming platform, it has some good games like Enigmo and Monkey Ball but those are merely ports and coincidentally are games that are perfectly suited for the accelerometer controls.
Heck the iPod itself had some pretty spiffy and high-profile games and no one called it a true portable console gaming platform, all those games look ok and not as cheap as some cellphone games but they don't even being to compare to games like Castlevania and Phoenix Wright, and those are games that were available on the Gameboy Advance, a handheld from almost 7 years ago!
I love the iPhone as much as the next guy but it's just that, a phone with one or two fun games, not a handheld gaming platform.