SAN FRANCISCO  If you want a smartphone powered by Google’s Android software, you could get Motorola’s Droid 2 or its cousin, the Droid X. Then there is the Droid Incredible from HTC, the Fascinate from Samsung and the Ally from LG.

That’s just on Verizon Wireless. An additional 20 or so phones running Android are available in the United States, and there are about 90 worldwide.

But if your preference is an Apple-powered phone, you can buy  an iPhone.

That very short list explains in part why, for all its success in the phone business, Apple suddenly has a real fight on its hands.

Americans now are buying more Android phones than iPhones. If that trend continues, analysts say that in little more than a year, Android will have erased the iPhone’s once enormous lead in the high end of the smartphone market.