Gohan was destined to become stronger than Goku in Dragon Ball and didn’t, just like Tails was meant to surpass Sonic the Hedgehog, but didn’t.
Every Dragon Ball fan is aware of Gohan’s great fall. His future was so bright, too. Even as a mere child barely able to walk, Goku’s firstborn was so strong that just getting upset caused his power to skyrocket off the charts. In fact, the first time Gohan saved the world, all he did was get really mad and yell at the immortal Garlic Jr., thrusting him into the Dead Zone.
But then Gohan peaked. Sure, it was one heck of a peak, but he never rebounded. During the Cell Saga, Gohan accomplished what his father failed and died in the pursuit of when he single-handedly defeated Dr. Gero’s ultimate droid named Cell (if you don’t count the fact that Goku helped his son from the beyond). Alone, this achievement is quite impressive. But in so doing, Gohan also became the first Saiyan to transcend Super Saiyan and achieve Level 2. Then Gohan got embarrassingly lame. The Great Saiyaman? Come on! Even his younger brother Goten and Vegeta’s similarly aged son Trunks surpassed him.
Tails experienced an eerily similar phenomenon in Archie Comics’ discontinued Sonic the Hedgehog comic book series. Way back in issue #56, a trio of highly evolved creatures called the Ancient Walkers first referred to Tails as the Chosen One and even regarded him as being more powerful than Sonic and Knuckles. It was later revealed that Tails had been chosen to defeat Mammoth Mogul, a massively powerful anthropomorphic mammoth who was one of the first creatures to become empowered by the Chaos Emeralds. Mogul was so convinced of Tails’ power that, while in a weakened state, captured and kept the twin-tailed fox perpetually transformed in his Turbo Tails state (Tails’ version of Super Sonic) and sucked the energy emanating from him over the course of 20 issues. In his place, Mogul created a fake Tails who lived with Sonic the entire time.
And then Tails peaked. In issue #150, Mogul amasses so much power that he goes on a rampage, destroying almost every single world within the multiverse in his quest for dominion. Luckily, the multiverse’s Zone Cop who monitors every reality gathers all of the Tails ahead of time to make sure he saved the right one. Turns out, they were all the right ones. Tails later merge with all of his counterparts and grow into a massive version of himself, who is luckily not only larger in size but stronger as well. Using his now gigantic twin tails as a reverse fan, Tails sucks the Chaos Energy from Mogul, allowing the villain to be trapped inside a Master Emerald. The irony is that when Mogul later escapes from his incarceration in issue #164, Tails does absolutely nothing and is essentially forgotten.
In Sonic and Dragon Ball, both the sidekick and supporting character who fans would have never thought in a million years would surpass their series’ main protagonists momentarily did before losing their powers almost as suddenly as they received them. Whether fans pressured the series’ creators to keep their main characters more powerful than the rest remains to be seen. Regardless, each franchise would have looked exponentially different had either Tails or Gohan become their series’ Sonic and Goku, respectively.