It occurs to me that the iPhone's sales tend to seem so impressive largely because there is only one model available. A company like HTC, or Nokia, or Sony Ericsson, will release a whole portfolio of devices with different strengths and weaknesses and greatly outsell the iPhone. If Apple did the same, release several devices at once (e.g. not stopped the first gen iPhone and released an iPhone Nano and iPhone Shuffle with the 3G), then their sales figures would also be split amongst several models and wouldn't give the false impression that the iPhone sales figures have given.
Obviously this gets writ large when OS's on mobiles are compared - with Nokia's Symbian and Windows Mobile far outstripping the iPhone OS. I can see the appeal of the iPhone, but I couldn't live with its limitations myself.