Thanks for creating this thread.
For the time being Android is the best os, but no one can say it's all time best as no one can guess in future what is coming, iOS has it's guts too, also I think WP7 will establish them very well as Microsoft is very trusted, and please exclude 'bada' from it, I am using it, it's most non supported OS and I am confident it has no future.
Regards.