Much debate has been made about fight between these two characters. But isn't the simple answer since virtually every debate on the subject includes the caveat of "No pre crisis Superman", that - at their best - Superman would defeat Goku?
Sure, pre crisis Superman is stupid powerful - with emphasis on stupid - but that's how he was written. And Sure the question of how Goku would fair against post crisis Superman is an interesting one. But, by even asking it you're making the concession at their best; Superman wins.