Yet another thread proving that ATOT has many a Super Nerd...
So I'll hop right in.
First, I voted for Goku, but only because I've been watching DBZ a lot on Cartoon Network lately. I personally don't believe that SSJ4 Goku would have an easy time defeating Superman, or vice versa.
But, I'm not sure where a lot of you people get your information on Superman, which is not surprising considering the plethora of available sources. So, to clarify, I'll just say that the Superman that I know is from the comic books from the late 1970's and early 1980's (before the first DC Universe restructuring). In these comics, Superman is a heckuva lot stronger than in any of the movies, and apparently a mega-huge amount stronger than now, if he really gets beat by Batman! In fact, I think the only fair comparison is SSJ4 Goku vs. Superman.
Let's just add up some abilities here:
1. Superman has heat-ray vision and super-cold breath. These basically go in straight lines from the point of origin. If hit by either of these weapons, Goku would undoubtably suffer major damage. If hit by super-cold breath, Goku would probably be frozen solid.
Goku has energy blasts including the Kamehaha blast, which can be guided after launch. If hit by this weapon, Superman would not be hurt. Superman routinely takes decontamination "baths" INSIDE the earth's sun after deepspace missions. Unless Goku's energy blasts are stronger than a couple of fusion megaton bombs per second, Superman wouldn't even notice.
Point: Superman
2. Superman and Goku both fly.
Point: Draw
3. Goku can teleport vast distances. It seems that he needs some small but significant amount of time (at least a second or two) to concentrate first (otherwise, he'd never get hit).
Point: Goku
4. Goku has died and come back to life twice in the episodes I've seen so far. Superman "died" once.
Point: Goku
5. Goku must "power-up," and depending on the power level, this can take up to a minute to do. Superman is constantly at his maximum power level.
Point: Superman
6. Goku can be sucker-punched (he was knocked out by Vegeta at the beginning of the Buu Saga), if he's not alert. So can Superman.
Point: Draw
7. Goku cannot breathe/survive in vacuum (outer space), which is why Frieza blew up planet Namek, so Goku would die. Superman can survive in vacuum for months if not years.
Point: Superman
8. Superman needs only a few minutes of very light sleep every few days. Goku needs normal sleep (since I've never seen anything to the contrary, I assume he needs 8 hours every night just like everybody else).
Point: Superman
9. Superman gets his power from our yellow sun. He retains his power unless he's exposed to a red sun. Goku needs lots of food. Preferably yummy. Goku gets weak if he doesn't eat a lot and often. Goku MIGHT be able to generate a red-sun energy blast but it's not proven, and there as many good arguments that he can't as there are good arguments that he can. If so, then Superman is toast, as long as the yellow sun isn't available (maybe in a cave or something).
Very Tentative Point: Goku
10. Superman wears tights and a cape. Goku has a bright orange Gi. Both have really big boots.
Point: Goku
11. Superman is "Invulnerable." His invulnerability does have its limits; he has gotten his butt kicked many times. Goku is really tough. But even as Super Saiyan 1, he got hurt when Krillin (a human) beaned him with a rock. In the same situation, Superman would not have been hurt at all. However, in terms of simply being able to survive a physical blow, they seem fairly even.
Point: Draw
13. Superman and Goku both have Super-Strength. It's very difficult to estimate their relative strengths because they don't perform the same feats of strength. Superman can pick up and throw skyscrapers. Goku picks up big fish and eats them. Hard to say who's stronger.
Point: Draw
14. Superman and Goku both have Super-Speed. Superman ran around the the circumference of the earth in a few hours in a footrace against the Flash. Superman flies to other parts of the galaxy (and somehow never encounters relativity effects) and back in a few days. Goku takes minutes to fly from one city to another. Again, this is hard to gauge, because he doesn't actually do this as SSJ4.
Point: Superman
15. Superman is "SuperSmart." That is, he is both brilliant, and thinks at Superspeed. He has invented many ingenious devices. He learned brain surgery by reading about it (at superspeed) and performed a successful surgery (that normally would have taken 10 hours) in 2 minutes. Goku has never been accused of being bright. In fact, some of his actions are downright stupid (i.e. giving Cell a sensu bean just before Gohan fights him).
Point: Superman
16. Goku knows martial arts. Of course, a lot of the leverage stuff doesn't apply when you're floating 50 feet above the ground. Superman seems to be more of a brawler. I think I remember references to Kryptonian martial arts, but Superman doesn't seem to use them much, if at all.
Point: Goku
17. Superman has an alter-ego he strives to hide from the public. Goku just avoids the mass media.
Point: Goku
18. Superman and Goku are both Super-Dedicated/Super-Stubborn. Both have refused to give up in hopeless situations where they've been pummeled to within inches of death, and have emerged victorious.
Point: Draw
19. Lois Lane and Lana Lang are a heckuva lot hotter than Chi-Chi.
Point: Superman
Hmm...after writing all this, I've changed my mind. My vote goes for Superman.
I think if they got into a fight, Superman would just freeze Goku and/or throw him into outer space where Goku couldn't breathe. Yeah, Goku could wish for some Kryptonite, but it'd take him a few months to round up all the dragonballs first. Assuming they just used hand-to-hand combat and stayed on the planet, I think it'd be a draw. Until Goku got hungry.