Interesting to point out that they actually didn't use Goku at his prime for this fight. If memory serves the manga chapter they used where Goku lifted forty tons was from the Buu saga. So basicly they took Buu saga Goku and slapped SSJ4 on him.
Now, Goku in GT was absurdly strong by comparison. For example, General Rildo is stated by Goku himself to be stronger than Majin Buu, yet Goku has no trouble fighting him in base form. What that means is Goku in GT is at least as powerful in his base form, as his SSJ3 form was against Buu.
So at his absolute maximum as a SSJ4 in GT Goku would be about 4000x stronger than he was as an SSJ3 against Buu.
However, I'm not arguing Goku should have won based on that. I'm just fine with them sticking to the level of power shown in Z . The utterly ridiculous power increase Goku is shown to have in GT despite being reduced to child form is one of the reasons GT is so hated. At least thats one of my reasons.
I don't mind them using SSJ4 for the video though, as SSJ4 was by far the best thing about GT, and the way its achieved actually makes some sense.
So yeah, canon Goku with SSJ4 can't beat Superman. Just thought that was interesting.
Also, fuck GT.
EDIT: And now that I'm thinking about it the whole 40 tons thing is bugging me. I know thats what it said in the manga, but it seems to be horribly inconsistent with the actual power Goku has demonstrated throughout DB and DBZ. Hell his own body weight would have been several tons when training under 100X gravity on his way to Namek, and by the time he fought Frieza he was vastly more powerful. And thats not even taking his weighted clothes into account. Although, he might not have still been using weighted clothes at that point. Memory fails me here.
I know Power levels are unreliable, but this should give you an idea of what I mean.
Goku VS Ginyu Force-90,000
Goku vs Frieza-3,000,000
So if Goku at 90,000 can move around in 100X gravity, then by the time he fought Frieza I would say 40 tons wouldn't be that much to him. I guess I'd just chalk it up to a mistake on Toriyama's part. Not that it really matters to the DBZ storyline.
It just bugs me.