What is the difference between an iPhone 3G and iPhone 3GS?

The 3G S has more features like voice recognition, a compass, video recording (with a 3 megapixel camera) and a GPS. You can also stream movies and TV shows straight to your phone in areas that have wireless internet.Also if you would like to compare the prices the iphone 3g cost $99.99 and the iphone 3gs cost $199.99.But i consider the the iphone 3gs is the best.