Hong Kong-based market research firm Counterpoint Research announced late yesterday that Apple's 2013 flagship phone became the world's best-selling smartphone in September, even though it was on the market for just 10 days. Starting on September 20, the iPhone 5s became available in nine countries including the US, and it outsold any other smartphone. The launch of the iPhone 5s made the Samsung Galaxy S4 drop to second place. The next spot was taken by Apple's iPhone 5, followed by the cheaper 5c.