Android users don't care about iMessage, they care about being able to communicate using modern technology with iOS devices. It is currently difficult to do this because of Apple. Despite having so many options, apple users prefer using the stock messages app because it's too difficult to download another app to communicate.
Guarantee you when RCS gets adopted (assuming apple does not do the bare minimum in terms of features), android users will no longer care about iMessage. Apple users might still care about the blue bubbles due to wanting to feel better about themselves for the phone that they purchase, but not android.
Look at Europe, do android users care about or want iMessage? No, because everyone uses WhatsApp. The only reason people in US care about iMessage is because apple makes the alternative suck horribly (SMS), so of course iMessage will be superior. There is no viable alternative like WhatsApp in America because apple users don't want to download it, so thus it's the choice between SMS and iMessage, and there is a clear winner.