ummm just to clear things up about the the bulma thing. She does know how to build one, cause your using an excuse from the movie, I can too right? well Bulma builds one in movie 12 to send Tapion home, besides that its one of the few movies where it actually fits into the timeline AND contributes to the story (how trunks got his sword).
Tech, goku could just go back to the day supes landed on earth and blow up earth lol.
This is how things works.
Goku's resistance to injuries as his invulnerability, stamina and durability in SSJ 4 are great, but when he was having problems lifting a building, was just after the fusion ends and he was left without less than 50% of his full SSJ 4 powers, and also he and Vegeta were fighting the last Dragon, that was hundred times superior to them.
But Goku during DB GT saga, has show his great resistance to injuries:
Take the Kame-Ha-Me-Ha throw by Baby/Vegeta to the Earth, a "PLANET DESTROYER CAPACITY" energy blast, something that Post Crisis superman cannot take.
I think that was the great feat of resistance to injuries he show during DBGT
I read a wrong affermation, Goku wasn't defeat by Cell 2nd transformation but from the Pefect Cell after he explode and then regenerate himself.Goku VS Majin Vegeta wasn't a real fight, cause Goku threaten himself from using his real power, the SSJ 3 form, if he choose to, Vegeta would be outmatched.
Goku needs help to defeat Chii-Bu cause the SSJ 3 form needs great energy, so Goku after hours of fight was tired and wasn't able to send back the Genki Dama if the Namec Dragon Polunga didn't recharge Goku that transform into SSJ form to send back the Genki Dama and finally destroy Chii-Bu.
If Majin-Bu wasn't able to totally regenerate if not hit by something like a Genki Dama or Vegeth disintegration beam(the beam he shows on the piece of head of Bu but didn't use) Goku SSJ 3 would finally beat him.
Goku has defeat Frieza ALONE, READ IT, ALONE.
1VS1, in SSJ form he finally disintegrate Freeza after he heal him after he was cut in 2 pieces from his Laser Blade.
About DBGT strenght feats, DBGT fights were crap, cause Goku was child so less powerful, and Trunks and Pan were to crap fighters too.
DBGT fights are more a Energy Blast VS Energy Blast fights except for Baby/Vegeta VS Goku and Goku VS the Sun Dragon Suu Scenron or Goku + Vegeta VS Li Scenron
Goku from SSJ 2 form to SSJ4 are too much for a Post-Crisis superman, probably a SSJ first level with a Kai-O-Ken is going to be hard for supes.
Anyway i like very much DBZ and only few fights of DBGT, but they are too much powered.
In Marvel and DC comics there are powerhouses heroes, like Supes, Captain Marvel(SHAZAM), Martian Manhunter,Thor, Hulk, Drax, Beta Ray Bill, their fights are great and outstandings but not a totally god-like with planets being destroyed when they blink and eye.