Only? That seems remarkable for this point in its lifecycle. It feels very much like there is still a product-market fit to be determined here and many app developers are likely still trying to determine how this new device fits with their product
That being said I don't know what the first "wow" app was for the iPhone other than games?
It was that beautiful touch screen + real apps, namely email and a browser. Before that, the number of devices with an email client not controlled by BlackBerry and a full on browser was very small.