On the heels of a recent study showing the Android platform losing ground in US marketshare to rival Apple, Canaccord Genuity has released data showing that Samsung's Galaxy S4 took the top seller position at three of the four major US carriers' outlets in May -- with the exception being AT&T, where the eight-month-old iPhone 5 continues to be the most popular model. The survey, which only checked direct carrier stores' sales of handsets, gave the S4 the top spot at Sprint, T-Mobile and Verizon, with the iPhone in second place at all three.