Each time I buy anything expensive I look at alternatives. This time around I don't really like Android, for it doesn't seem as polished as iOS. It reminds me of how early versions of Windows stacked up to MacOS. Also, I distrust Google. As others have said, we are not Google's customers – marketing companies are – and I worry about what private data Google is 'mining' from me.
I have yet to look at a Windows phone, but I tend to want cutting edge systems rather than bleeding edge ones.
However, maybe when I update 2 years or so after I get the next iPhone, I'll consider an Android or Windows phone (funny how nobody ever seems to mention that possibility). Maybe even Blackberry will have something that I like by then. Any phone that would lure me away from Apple would have to overcome Apple's advantages with respect seamless interoperability with the MacOS environment.
'What's right isn't always popular: What's popular isn't always right.' - Howard Cosell
I guess it boils down to how one defines '#1'... Fords are more popular than Bentley's...