Superman is stronger than any of Goku's ssj tramsformations and would prabably be able to kill him with less that ten hits but in combat Goku is much faster. Superman may be able to fly at the speed of light but no one can recall the last time that he fought at the same speed as his flight or even at Dragonball combat speed. Also because Goku was thought marshall art it gives he is able to dodge and counter Superman's attacks as when it comes to fighting Superman relise on his brute strenght. It is said that Superman's only weaknesses are kryptonite and the destruction of the sun which fuels his energy giving him unlimited duration and obviously Goku Isn't intelligent enough to realise that concluding that he will attempt to take him on head on. So if Goku is fast enough to dodge Superman's attacks and Superman can obviously handle Goku's physical attacks who is going to win. Well I believe that Goku can easily overwehlm Superman's defence with dragonfist as his ki attacks would most likely damage Superman too much. If the planet that they are fighting on gets destroyed Superman's only chance of winning is restraining Goku from instant translocating his way to a planet that supplies oxygen which will result the battle to a draw unless they fought in Other World then Goku would win. So what do you think Kal-El or Kakarrot?