Easy. It's a phone. But hey, like I said, that's easy. For a more complicated answer, why don't we see what VP of iPod and iPhone product marketing Greg Joswiak has to say.
In a departure from some of the company's more boisterous, were-gonna-git-you-DS claims, Joswiak tells Edge that the DS and PSP are from the past. And the iPhone? You guessed it. It's from the future.
I think if you look at devices like the DS and the PSP, in a lot of ways, they've defined the past in handheld gaming, and I look at a product like the iPhone with the App Store, and I think it has the opportunity to redefine the future, from everything to how you acquire games - not to mention updating apps.
How do you update a cartridge? You can't. But you can update the games here via the App Store and that's an automatic process. Not to mention not having to carry around a bucketful of cartridges. You can store as many games as you have space for. Everything about the iPhone suggests where the future's headed, and I think a lot of the other guys are trying to scramble for what they do in response.
He may be right! After all, the PSP is quietly moving to a digital distribution model for many of its games.
Then again, people don't appear to be holding off on purchasing a DS because of the back-breaking labour involved in carrying "a bucketful of cartridges" around.
In Defence of the iPhone [Edge]