The Top Two Selling Smartphones World-Wide are iPhones
Strategy Analytics has taken a stab at estimating iPhone 4S sales versus iPhone 5 sales from Apple's reported aggregate iPhone sales (Apple does not break down sales by model). They have of course estimated the number of units sold for other smartphones as well (since most manufacturers don't report quarterly unit sales numbers).
Their report suggests that the #1 selling smartphone is iPhone 5, followed by iPhone 4S. Third place was awarded to Samsung's Galaxy S3.
Source: Strategy Analytics