> "Five years ago, the Motorola Razr was the top-selling phone," says
  > Credit Suisse analyst Jonathan Chaplin. "Imagine trying to sell 6 
  > million of them today."

The thing about the RAZR is that it was a sleek, small form factor. I don't remember anyone who had one tout its functionality as the reason they got it. So the next sleek phone or better featured phone could easily displace it. The iPhone on the other hand combines excellent engineering of its hardware with tremendous strength in the software; not to mention the brand cachet. That's a significant competitive advantage and is harder to displace.