Apple’s aging iPhone 4 and iPhone 3GS were the best-selling phones in Q2, says NPD Group

Apple’s iPhone 4 first launched in June 2010, and the iPhone 3GS came out in June 2009. But in the three months ending in June 2011, they were again the two most-purchased phones by U.S. consumers, according to NPD Group. And Apple isn’t the only one getting mileage out of its devices: The third-place device, Sprint’s HTC Evo 4G, first launched in June 2010, too. This all despite dozens of new smartphones from a handful of competitors.

Here are the top five best-selling phones during Q2, via NPD’s Mobile Phone Track service:

1. Apple iPhone 4
2. Apple iPhone 3GS
3. HTC EVO 4G
4. HTC Inspire 4G
5. Samsung INTENSITYII

Things to consider: The Verizon iPhone 4 didn’t launch until this year, and Q2 was its first full quarter of availability. The white iPhone 4 just recently launched, too. And the iPhone 3GS has continually seen price cuts at AT&T, as it will likely be retired this fall. But still, in an apparently rapidly evolving field, the technology behind these phones is one and two years old.

Related: The iPhone 4 gets better with age