For the record, Dragonball gods are inherently flawed because they have LIMITATIONS.
Or have you all forgotten that the original Shenron (dragon god, remember?) outright stated he couldn't even remove the explosive from C18's body? And C18 was a mere cyborg, powerful all you want, but still largely man-made.
If a cyborg is stated by a so-called 'god' to be more powerful than he is, then that 'god' is pretty damn wimpy. And I'm not even going to address how gods in DBZ are more akin to Marvel 'gods', as in extradimensional beings of great power, but still ultimately mortal.
Now, Superman kicks extradimensional beings of great power's asses on a regular basis. Why should a DBZ god be any better than one of those? Hell, I'd argue Darkseid is more powerful than any of the Kais, given how he was stated to be a blight upon the entire multiverse by a few sources in DC...
That taken into account, Superman wins simply because he can just grab Goku and drag him in outer space. The ONLY confirmed Saiyan who can survive in outer space was Broly, and he's from a filler movie. DBGT is worthless, as like the Broly movie, it wasn't made by Toriyama, and Toriyama has been put on record as saying he didn't like it to boot.
The fact Supes can go in outer space and not die, while Goku can and will die gives him a pretty damn huge advantage. And Supes survived a direct hit from Darkseid's Omega Beam, which up until that point had outright obliterated anyone it struck regardless of power, so he's pretty damn tough when it comes to taking beams o'doom, which reduces the Kamehameha's usefulness...