The nexus s came out in 2010. They had to update the 3gs because they still sell it. They stopped making the nexus s a while ago.
the point I was trying to get at is that I found an old ipod touch and gave it to my daughter and I was surprise that I could update to iOS 5 and get some of the new stuff like imessage etc.
Android is fragmented and with so much different manufactures competing like samsung and HTC to be the best android smartphone makers, the android consumers will get left behind all the time as a 1 year android device will get obsolete and probably wont see an update on that phone especially if that device is tied with an network operator.
Its not about android fanboys and aple fanboys, but I can still keep my iphone 4S for another good 1-2 years without feeling like my device is old and left behind when it comes to software updates.