A new Apple iOS device usually receives OS updates for three years. Without breaking it down, to quote Ars Technica's review of iOS 7, posted today: "The length of the iOS device support cycle remains about the same as it has been for the last couple of years. If you buy an iOS device when it’s brand new, you can (with some notable exceptions) expect three to four years of software support"
Microsoft didn't support upgrades from Windows Phone 7, which is three years old, to 8. 8 isn't yet three years old.
Taking Android's case at its strongest, Google provided updates for the Nexus One for less than two years — from the January 2010 launch of the phone until the October 2011 release of Android 4.0. It provided updates for the Nexus S for only very slightly longer — from a December 2010 launch through to the November 2012 release of Android 4.2.
The Galaxy Nexus and Nexus 4 have received the latest versions of the OS. The Galaxy Nexus will be two years old in November.
So at the very least, Apple devices are definitely not doing worse than the market average.