One thing could be unique chakra abilities. If in a fanfic, Naruto discovers a new form of chakra that gives him unlimited power, he could be stronger. For example, a chakra that can nullify all energy - based attacks like Goku's ki blasts.
Maybe some kind of special bloodline limit. Suppose Naruto gets a new bloodline limit in a fanfic that allows him to absorb and redirect any kind of energy. Since Goku mainly uses ki energy, Naruto could use this new ability to defeat him. Also, if Naruto has some sort of reality - warping chakra ability, that would put him above Goku in terms of power in a fanfic.
In some fanfics, Naruto can be made stronger than Goku. Fanfic writers have the freedom to manipulate the power levels and abilities of characters. They can give Naruto new and overpowered abilities that surpass Goku's. However, in the original canon of their respective series, Goku has extremely high power levels and abilities that are on a different scale.
Well, in this kind of fanfic, it's not so simple to decide who is stronger. Goku's power levels keep increasing exponentially as he reaches new super saiyan forms. He can destroy planets with his power. Naruto, though, has the ability to harness the power of the nine - tailed fox which is also extremely powerful. Moreover, Naruto has his own unique chakra - based attacks. If they were to fight, Goku might start off with an advantage due to his speed and power. But Naruto is a very quick learner and could adapt during the fight. Also, Naruto has his friends and allies that could potentially tip the balance in his favor in a more complex battle scenario.
In fanfiction, it's possible for Naruto to be stronger than Goku. Fanfic writers often tweak the power levels and rules of the characters' universes. For example, if the fanfic writer decides to nerf Goku's Saiyan abilities while enhancing Naruto's Sage Mode and all his ninja skills to an extreme level, Naruto could end up being stronger.
In a Goku Naruto crossover, both characters have their own strengths. Goku's physical strength and energy attacks are off the charts. His ability to instantly teleport and sense ki gives him an advantage in combat. Naruto, though, has a unique power system. His connection to the Nine - Tails and his ability to use different types of chakra make him a force to be reckoned with. If we consider a battle, Goku's power might seem greater on the surface. But Naruto has the advantage of being able to surprise his opponents with his ninjutsu and clones. Also, Naruto has a strong willpower that has allowed him to overcome many tough situations, which could play a role in a fight against Goku.
One reason could be the variety of his abilities. Naruto has a whole range of jutsu like the Rasengan and Shadow Clone Jutsu. In fanfiction, these could be made extremely powerful. For instance, if his clones could multiply infinitely and each had the power of the original, that would be a huge advantage.
In most cases, they are depicted at similar levels of strength. But it can vary depending on specific story arcs and interpretations.
In most cases, they are considered equally strong. The power levels in both the anime and manga are often presented in a similar manner.
Goku is known for his raw power and his ability to constantly increase his strength through training and battles. He can blow up planets with his attacks in his more powerful forms. Naruto, on the other hand, has the power of the Nine - Tailed Fox and his own unique ninja skills. But if we consider the fact that Goku can move at speeds close to the speed of light and has energy attacks that can obliterate entire solar systems, he might seem stronger. However, Naruto's ability to use shadow clones to outnumber his opponents and his Sage Mode which gives him enhanced perception and strength can't be ignored. It really depends on the situation and how the author of the fanfiction writes the encounter.
Well, Naruto has had the advantage of learning from many great shinobi over time. He also has a unique bond with his friends which could potentially give him more strength. Minato, on the other hand, had a shorter lifespan to develop his powers. Naruto has had more time to grow and surpass his father in strength.
In most cases, Goku is stronger. However, Vegeta constantly trains and has shown the potential to match or even surpass Goku on certain occasions.