I was wondering this today too. In all probability the iPhone 5 will be running the same CPU/GPU as the iPad 2, which will probably be the dual core A5 chip with a PowerVR SGX543 (perhaps in dual configuration). Last year the Samsung used the same chip as the iPhone 4 but a PowerVR SGX540 instead of the iPhone 4's SGX535 so it was a bit more powerful.

This year it's a bit different since Samsung has decided to go with the ARM Mali (in some sort of multicore setup) which no one has any experience with really. Maybe apple has bought so much of samsung's chip that it left none for samsung themselves to actually use in their galaxy 2 lol.