Why is the iPhone so successful? I believe the most important reason are Apps.
Why are other Smartphones as Blackberry losing market share? I believe the most important reason, again, are Apps.
Why is Android generally only considered to be 'second choice'? I believe the most important reason is that the Apps are not of the same quality. No way its because of the OS - Android is fantastic. Also not because of the phones. Some of the HTC's may even be better than the iPhone.
The difference are simply Apps.
The slick User Interface and the unbelievable usability of the iPhone in particular and other Smartphones with Touchscreen in general are only the foundations for funny, entertaining, supporting and intelligent Apps and the full user experience.
This and the upcoming Mac App Store (eventually followed by an equivalent Windows market) are reasons enough to think about the role Apps play nowadays. By the way, I purposely call them Apps and not Applications or anything, because in my view, they are no fully featured Applications, but well, simply Apps. They serve a single purpose or fulfill a few very specific Tasks (Hotel Finder, Flight/Train Connections, Facebook, Weather). I don't think I use any App for more than 2-3 minutes per session (maybe some games, but by far not all).
The fact that, so far any mobile Web Browser sucks in some way (Surfing the Web on a Smartphone is horrible, all this zooming and scrolling and totally naked "mobile optimised" Websites) and the fact that I have around 100 Apps on my phone which are all little helping goblins made me believe that Apps are actually the librarians of the World Wide Web.
This is totally awesome, because instead of starting your notebook, starting your Web Browser and opening a few Tabs to look for a route or a restaurant near your girlfriends place you just use an App, what is just way more convenient.
Most (helpful) Apps work as follows:
a) They offer you a simple and clean GUI (sure, they are built around 1 main functionality)
b) They search for what you want, through the whole Web, through APIs, through everything
c) They neatly display you what you wanted
After that process which perhaps took around 40 seconds, you close the App and are enlightened. I think this is the same as a librarian is doing:
Most (helpful) Librarians work as follows:
a) They offer you a human UI (you should be able to get on with that)
b) They search the whole library for what you want, or give you further information on where to find your desired stuff
c) They give you what you wanted (Your books or at least a note with some further information)
I think Apps are the main reason why mobile internet is so exciting and popular nowadays. Simplicity and information rich, just a tap & swipe away. And Apps really are a driving factor of the semantic web (lots of stuff is communicating via APIs with each other) as well, because thats pretty much the essence of their workings, you tap search and the App is doing the rest.