Apple have thrown an update to their iPhone page that details the three generation of iPhone available for sale at the iTunes Apps Store. The Page compares the speed to iPhone 4S using A5 Dual Core Processor along with iPhone 4 using A4 Chip processor. The iPhone 3Gs uses only 3 Mega Pixel camera, iPhone 4 has 5 Mega Pixels Camera while iPhone 4S uses 8 Megapixel Camera. The prices are also listed along with size dimensions and prices for various models.
Just see a screenshot of the page and click on the image to enlarge it