What does that prove? Anyone can get any engine running on the iPhone/Pod/Pad, but that doesnt mean they magically (see what i did there?) have good controls that dont require your fingers to cover a large portion of the screen. It doesnt magically give the user tactile feedback. It doesnt mean anything other than Unreal runs on the i<device>.
If someone could get Halo 3 running on the i<device> at 60 fps with full online capabilities doesnt mean its going to be fun to play. Its going to suffer from the same problem as Chinatown Wars: console controls clumsily fit onto a touch screen.