Come on guys, Kamé Sennin destroyed the moon with his Kamehameha. He didn't only break it in half, he turned it into dust, so imagine the power of that Kamehameha.
My point here is, Kame Sennin may be weaker than Superman, they're still close in power. Goku is totally out of his league.
Remember that Goku beat Buu, a monster so powerfull that he killeds 4 out of 5 gods of the Universe and could probably destroy every living thing in the Universe.