Well, I say we compare their abilities and things we know about them. (note: for Superman, I'm using Stilts' article found
here... when I quote something for Superman, it is directly from this website)
Speed:
Superman: "Many times the speed of light"
SSJ4 Goku: Instantaneous (and, yes, he uses this in fights)
Winner: Goku
Strength:
Superman: "he possesses the strength necessary shatter entire worlds" (I'm taking this to mean he punches the ground and the earth breaks up)
SSJ4 Goku: Unknown... I would assume rather close to Superman or equal being that he could destroy entire mountains by punching them at ssj1 (or before ssj1, depending on the size of the mountain).
It is also known that ssj2 is
many times more powerful than ssj1. SSj3 is many times beyond ssj2 and
ssj4 is at least 10x more powerful than ssj3.
Unfortunately, we don't know how strong these transformations are when compared to what Superman can do. However, I think it can be inferred by this evidence and some circumstantial evidence shown to us in some episodes (I'll give some if asked for) that SSJ4 Goku would be equal in strength to Superman, slightly stronger to Superman, or slightly weaker than Superman.
Winner: About Equal
Ranged Attacks:
Superman:
Heat Vision: Superman can emit beams of heat energy from his eyes with "heat that rivals a star" which he can use to vaporize one or multiple opponents.
Super Scream: "In one instance, Superman was shown to have the ability to project a "super scream" from his vocal cords. He used this ability to cancel out the impending threat of an already exploding nuclear detonation."
Super Breath: Superman can create hurricane-force winds and can freeze things with his breath.
SSJ4 Goku:
10x Kamehameha: Given that a normal Kamehameha from Master Roshi can snuff out a burning mountain, and that a Kamehameha used against Cell at SSJ1 was said to be able to "destroy the earth." This attack also has an after affect where the target is paralyzed for a few seconds (it probably disrupts their nervous system). I'd say, the 10x Kamehameha is more powerful than Superman's Heat Vision (if it's possible to be more powerful than vaporizing something).
Spirit Bomb: This would not work on Superman because it can only harm those who are not pure of heart and Superman is the ultimate Boyscout. However, if Goku could get enough time to use this, he could absorb it as seen in the
Super Android 13 movie thus increasing his strength depending on the size of the Spirit Bomb.
Winner: I'm not sure, they might be about equal in destructive power, but Superman has more variety. If (yes "if") the paralyzing affect of the 10x Kamehameha affected Superman, it would give Goku the advantage.
Durability:
Superman:
Healing Factor: If Superman is harmed, he can heal almost instantaneously.
Nigh-invulnerability: Superman has an aura a few millimeters from his skin that protects his body from harm and has a much denser body structure than that of a human.
SSJ4 Goku:
Nigh-invulnerability: Let's face it, to be able to fight people who are almost as powerful as as an SSJ4, you have to have great durability. Goku has been shown to take multiple punches from people who are about his level and who are stronger than him and keep fighting.
Winner: Superman
Superman has a major advantage because he can heal himself. Goku, on the other hand, cannot. Although this healing is a major advantage, Goku has fought beings who could heal themselves and bested them (Cell and Majin Buu). If Superman fought ssj4 Goku, his healing abilities would be put to the test.
Stamina:
Superman:
Solar Energy Absorption: Superman gains his power from yellow Sunlight. When in yellow sunlight, his healing factor kicks in and he's healed. It is also due to this energy coursing through his body that he gains all of his powers.
SSJ4 Goku:
Strength of Will: Goku seems to have stamina through sheer strength of will. During most of his fights when it looked like he would die, he kept fighting despite his injuries (there are logical limits to this, of course).
Winner: Superman
If the fight becomes a stalemate, Superman will win because he will not tire.
Please post any more comparisons you have in a similar format so we can look at this some more. I'll post my opinion as to who would win when I think I've heard enough arguments.