Here's what I think. I'm going to use 3 example.
I'll be using the core character, I know superman even has a evil backstory where he kills people. However for the sake of comparing them I will use the Core Idea of the man we call superman.
1. Goku - A Fighter who overcome his weakness and become stronger to defeat any challenge.
2. Superman - A God who has been proven so many time to have limitless power but want to be a human. his kindness lead him to not wanting to use the full extent of his power. On anyone in fearing of hurting or killing another cause of his overwhelming power.
3. Batman - A Genius that seen the worst in the world, Take the world as it is and try to protect it at all cost.
If we're going to compare Goku & Superman powers in term of levels or what they can do it won't work. They simply live in different universe that you cannot calculate. Simply because There is to many superman backstory so many different take on superman, as for goku there's only one of him. So we ruled out measuring powers.
Now we begin on how can batman beat superman? Superman is kind and naive he WILL Let himself get in danger and harm ways because he is to kind to everyone even bad guys. No matter how smart a man batman is, in a matter of seconds superman can fry his brains. But superman will not. However Batman will if he believe that is the way to save earth.
So how does this relate to how who would win in a fight between goku and superman?
Now that we know both personality. we can began to guess how they would act toward each others.
Goku would fight it all out with superman and superman would let loose as much as he can without killing goku. Superman would never kill someone with a innocent drive to become stronger, In short they would be the best sparring partner.
I will say Superman will probably not lose for a while but Goku is a man that overcomes everything. Thus why I believe, Goku has the potiental to be stronger then Superman. Goku has the drive to become stronger and better. Superman just wants to be a god that lives along side human.
Thus in conclusion a tie.