My theory is that the vast majority of people didn't need/want all the capabilities of BB/Symbian, and instead chose the iphone for its ease of use, or because their friends had one, or as a fashion gadget. Same with the car analogy, most people don't buy a car based on how well it accelerates and corners, hence the Camry outsold the RX7, but it doesn't mean the Camry was superior.
Well the iPhone to me was the first with a real good touch interface. Apple has always struck home with a good hip product. The iPod already had like 85% of market dominance. If you look up all the other products it competd with like the Creative Zen, Nomad, Dell DJ, whatever the hell you want to name, all those products gave better battery, or even removable battery, better storage, better pricing..
But none had a good UI. The scroll wheel was still THE BEST way IMHO to navigate through the iPod. DPads, scroll wheels, vertical touch lines... what the hell were people thinking? The iPod had a good form factor and was small enough to carry everywhere easily.
The iPhone did less than many WinMo or Symbian phones. I listed like 20 features I could easily do on my phone that even today many phones lack, but that's not the point. People wanted to try something easy.
In the end I don't think its about features and capabilities. I think it's the reason I got a Mac too. In the end I can summarize 90% of my day as surfing, chatting, social networking, word processing, reading PDF documents, spreadsheet work, ppt editing, and all that can be done on a Mac just as easily as a PC. I could argue that today I want to flash my Crucial M4 SSD and that the easiest way to flash is to use the Windows 7 flash utility and it does it all automatically. But how often would I need to flash my SSD that my Mac presents SUCH a big restriction? Not that often.
So I guess its the same with the iPhone. If you surf, text, read your emails a lot at that time, the iPhone was enough. You could accomplish most of what you do on any other smartphone but do it in a NEW manner...touchscreen. I think that was enough to sell a good chunk of the crowd.
I on the other hand stood far away simply because I wanted to hold onto my features. How often did I tether? How often did I need my Xenon flash? Those are things I could live without and not really regret it honestly.