That doesn't change the fact that people who bought a 3GS 2.5 years ago are still getting significant updates to the hardware. Really, what better way is there to support a product than continue selling it?
If you want to look at the other options out there, Android is doing a terrible job. A number of Android phones don't even ship with the most recent version of the OS and some never see updates at all. It's getting better, but it's far from great.
But it doesn't -- there are many Android headsets that were obsolete when released (OS-wise) and then never updated. The situation with Android devices (at the high end) is getting better but it's too early to see what the situation will be like in 3 years.
If you want to look at the other options out there, Android is doing a terrible job. A number of Android phones don't even ship with the most recent version of the OS and some never see updates at all. It's getting better, but it's far from great.