The screenshot above comes from the iPhone 4-specific version of "NCAA Football," which costs a $7.99. The screenshot below comes from the non-iPhone 4 version of the game, which costs $6.99. The difference is subtle, but noticeable, as the above image definitely features higher resolution graphics, but do we really need another way to divide the App Store?
Before the iPhone 4, the App Store was divided into iPad and iPhone games. Certain games took advantage of the boosted 3GS hardware by scaling the graphics based on the system (as was the case with "Space Miner,") but we haven't games exclusive to specific kinds of iPhones yet.
It's unfortunate because the App Store has always been pretty straight forward and easy to browse, unlike the other mobile markets that came before it, which were bogged down by system requirements and phone-specific versions.
It'll be interesting to see if companies follow EA by releasing two separate versions, or whether they'll just update the current versions to scale up to the new hardware. Firemint has already announced that "Flight Control" and "Real Racing" will be updated with iPhone 4-resolution graphics, but it's currently unclear whether those will be require iPhone 4-specific apps. Here's hoping not. The App Store should be one giant melting pot!