Exactly. Piccolo, Goku, Vegeta, Gohan, Goten, and Trunks are all absurdly powerful by anyone's standards. Mortals simply aren't meant/expected to become that powerful, but then these three had special advantages. Being Saiya-jin (thus having "Zenkais" and Super Saiya-jin), training with gods, coming back from the dead, all kinds of special training, and so on. I mean, remove the DBs and Goku's power growth ends at 416, Vegeta's ends when Freeza kills him on Namek, Gohan's likely ends on Earth against Nappa without Goku there to save him. Most people don't get another chance at life. Goten and Trunks are the kids of two of the strongest in the universe (and power seems to be hereditary in DB) and Piccolo's a twice fused being.Really, though, the people who think that the Gods (at any level) are useless need to remember that the main characters in Dragonball are huge anomalies. It isn't like each generation has people who could kick the crap out of the Gods.
Plus there's the gravity training they did, that no one else seems to have done, their superior understanding of ki, the RoSaT, various power-ups, the list goes on and on. They had dozens of advantages over the 'average Joe' of the universe to get them to that point. Meanwhile Freeza dominated the universe at a power of 530,000. Oozaru Vegeta was the second most powerful person in the universe when he showed up on Earth (180,000) and Ginyu the third at 120,000. The rest of the Ginyu Force were somewhere around 40,000. This is the more standard fare for the universe and the Kaioshin could just snap their fingers an kill them without training. Only those with all kinds of special help could get anywhere near them.






