I think when it comes to music and art it's debatable. Math/theories on the other hand is mostly fact when proven. So would be considered an artist in this modern time who could imitate and paint just as good or better than Leonardo or Michaelangelo a genius? They might be a master at their craft but a genius? I think to be a musical genius you have to be very creative and original and not a one hit wonder or happen upon one great piece by accident.
Music these days is very subjective, disfragmented into many genres, and woven into the fast pace of pop culture to expect a person of today to even recognize an endearing musical icon such as Mozart, let alone call him a genius. A rap lover maybe able to discern souljah boy's music from Tupac, but wouldn't be able to tell who composed Eine kleine Nachtmusik if they listened to it.
Yeah you raise a good point. I guess it's hard to compare science/math to something more subjective like art. And it seems like a lot more appreciation goes into past scientists/mathematicians than artists. Without the work of Newton, Galileo, even Aristotle, we might not be where we are today. Just the same, I think the case could be made that without composers like Bach, Mozart, etc. we might not have the popular music we have today, though it'd be a lot harder to directly see. Really, I don't have a good answer for you at the moment. I mean, there are plenty of anecdotes about his amazing ability in composing and playing that people might think indicative of genius, like the example I mentioned earlier where all his compositions would be planned out in his head before he ever wrote them out, but that's something that could be objectively called genius.
So, the Einstein/scientist people can be geniuses but the Mozart/artist people can't? So, only the Left brain can create genius work, but the Right brain can't? Is that the argument?