gta China town wars looks really cool actually, we don't get stuff like that on the iphone, yet.
Iphone isn't a real gaming platform. Motion controls are gimmicky and imprecise, the Iphone screen is so small relative to my thumbs and forefingers that touch controls are difficult for things involving accuracy, and no usable physical buttons make the whole thing suck for anything more than casual waiting-for-something gaming.
I really would rather have a GBA than an Ipod Touch or Iphone when it comes to gaming. Now, the Iphone far outshines the DSi simply because once you quit out of your gimmicky game, you can do so many things with your Iphone that it totally justifies owning one.