There are a lot of metrics to measure smartphone dominion among different smartphone brands and operating systems. Survey organizations use sales figures, net profit, internet traffic, apps ecosystem, etc., even broken down into different demographics and/or geography, to demonstrate the different systems’ leadership above the rest.
But, really, if you are going to be realistic about it, try going to restaurants, malls, and/or coffee shops around the metro, and observe which smartphones are predominantly in the hands of other people around you, you’ll find that these statistics are not quite accurate.