Sure some of the people in DBZ can blow up planets. Buu did, Freeza blew up Vegeta with no problem he just didn't want to kill himself so he didn't destroy Namek the quick. He figured he'd be gone, and stuff by the time it blew. Vegeta had a specific blast for destroying planets which was his Galic Gun. Cell only destroyed Kaiosama's planet not that big of a deal and it didn't even harm snake way at all. (Not going to go into Broli and the other movies since they aren't canon) But big deal they do it with ki blast.
First we're using the Superman of now not Pre-Crisis right?
Post has been knocked through the planet, and around the planet twice with punches and still was just fine. Stronger then anything that has happened from a punch from anybody in the Z world. A demon called Etrigan knocked Superman from Earth to Moon and he was still able to get back up and fight. He was hit by a blast on an alien planet that was said a force of a million nuclear bombs and turned everything around as smooth as glass and he still got up though a bit dazed afterwards. He was inside a moon when it was blown up by nuclear devices planted on it while in the future. Superman has survived in the sun..Though in All Stars Superman he's dying cause of a trip to the sun giving him to much solar radiation but he's still been able to escape its gravity which is a lot more then anything Gokou has trained under.
Superman has punched Lobo from Earth into space and Lobo is as strong if not stronger then Superman is. Fighting Doomsday when they punched each other shockwaves destroyed building around and were felt all the way to Gotham. (Though sometimes the comic make it seem they aren't far away while others they are far away but still) Superman has actually became intangible by moving his body so fast unlike Gokou who just looked it cause he moved that fast. Superman has also went from Earth to Saturn in 4 minutes and while doing it split a moon of a planet (Not Earth) in two pieces with sheer power.
Gokou hasn't done anything close to any of that. Nor has any of the people from DBZ.