The popular ROCK BAND [iTunes link] console game has been ported over to the iPhone/iPod Touch. So far, from the reviews on the App Store people are overwhelmingly happy with it. People are always going to whine about the price of a game if it's $9.99. It also seems to have performance issues if you haven't rebooted your iPhone. This is a game that would probably play much better on the 3G S.
The one interesting feature is that you can have multiplayer games through Bluetooth. Yay! No Wi-Fi needed!
I already have DanceDanceRevolution S, Saturday Night Fever and Tap Tap Revenge 2 so I'm not crazy about getting this type of game. Electronic Arts ALWAYS has a price reduction so I'll probably wait for that.
Meanwhile, don't hold your breath for Guitar Hero on the iPhone. Activision has not yet made apps for the App Store while Electronic Arts is already an App Store veteran.