The iPhone 4 has a much better camera than that of the iPhone 3G. The iPhone 4 has a five megapixel camera, while the iPhone 3G has a three megapixel camera. The iPhone 4 also has the capability to do face time video chatting.
Everything is b.e.a.utiful on the retina display. Im on mine right now and its astonishing how much cleeror things r on it compared to my old 3G. It looks like theres a haze or somthing then i try looking at my old phones screen :P