Goku is typically the strongest hero in Dragon Ball, but that may change in the next anime, thanks to Dragon Ball Super: Broly. Dragon Ball is full of incredibly strong heroes who are always gaining in power, and Goku is usually at the head of the pack. The Cell Saga in Dragon Ball Z shifted away from this, by positioning his teenage son, Gohan, as Dragon Ball's strongest character, but as Gohan slacked off on his training, the series returned to the status quo, and its remained that way ever since.
In 2018, Toei released Dragon Ball Super: Broly, which became one of the highest-grossing anime films of all-time. The movie takes place after the conclusion of Dragon Ball Super, which ended with Universe 7 defeating Universe 11 in the Tournament of Power. After three movie appearances, the new film finally makes Broly canon and essentially reintroduces the character. Broly was portrayed as an abnormally strong Saiyan who was exiled to a distant planet by his own people. Years later, Frieza thrusts him into a conflict with Goku and Vegeta, who are pushed to their limits by Broly. It takes their fusion form, Gogeta, to beat Broly.
The movie does something with Broly that none of his non-canon films have attempted with the character. Dragon Ball Super: Broly turns him into a misunderstood character, and provides him with depth for the first time. It's clear that Dragon Ball Super's take on Broly isn't evil, nor is he even a real villain. He's a man with a somewhat innocent nature whose immense power is exploited by people like his father and Frieza who seek to use him for violence. At the end of the movie, Goku and Broly are no longer enemies, and Goku even expressed an interest in sparring with Broly in the future.
Where Dragon Ball goes from here isn't quite clear, but the franchise is expected to continue in the form of a new movie, and possibly as a new anime series as well. One of the biggest questions concerning Dragon Ball's future is where Broly fits into Toei's plans. Dragon Ball Super: Broly sets up Broly as a heroic character, which could mean he'll find himself on Goku's side when the next threat emerges.
Since it took Gogeta to stop Broly, Broly is clearly superior to Goku in terms of power, which would make it interesting to see how a future TV series or movie would handle the character. If Goku is put in a situation where he once again has to gather Universe 7's most powerful warriors, Broly seems like the most obvious pick. If Broly were to return as a hero, Dragon Ball's protagonist may find himself playing second fiddle to the Legendary Super Saiyan.