Androids typically only get 1 or 2 updates before their manufacture stops updating them as well. I say this coming from a droids, htc's, and currently a S3.
the difference is, app makers know the market share for even android 2.X is still very large, meaning when they develop apps they make sure it will work on older versions of android.
so in the end mobile apple products will be supported by apple for longer then most android products by their manufacturer. BUT, android developers will more likely support older android devices then they would older apple devices. at least thats how it seems as of now.