One of the many reasons fans are enjoying Boruto: Naruto Next Generations is because they get to see Naruto at his strongest, after years of watching him struggle to get stronger in the first anime.
But his increase in strength over the series was best shown in the final episodes of Naruto: Shippuden as his fight with Sasuke brought out everything he had.
Just realized this attack is basically a combination of every single technique Naruto learned throughout the series. from r/Naruto
The final fight of the series has both Naruto and Sasuke going all out, and using every technique and skill at their disposal in order to defeat one another. The fight is fondly remembered by fans for not only its callbacks to previous fights in the series, but the landscape of the fight as well.
One of the inside jokes among fans in this final fight between Naruto and Sasuke is that it basically becomes a super mecha fight scene. As demonstrated by the clip above in which Naruto gathers everything he has within Kurama, and uses his Shadow Clones at full Jinchuriki state to build giant chakra blasts.
Sasuke, of course, responds with a giant power of his own and the two clash in a way that has yet to be matched in the entirety of the franchise. But Naruto's growth is the main reason kept going back to the series for years, so it seemed like the only way to perfectly capture the intense growth he underwent was go all out with a mech-like fight.
Although not completely reflected in Boruto, Naruto had essentially reached god hood as he fought with all sorts of powerful beings toward his series' end. Fans knew that his struggle to control the Nine-Tailed Fox's power was going to be fun to watch, but no one expected to see how strong Naruto truly became in the end.
For those unfamiliar with Boruto's predecessor Naruto, it has quite a storied history. Originally created by Masashi Kishimoto, the series ran in Shueisha's Weekly Shonen Jump for 700 chapters. The story follows Naruto, a young ninja with a sealed demon within him that wishes to become the leader of his home village. The sequel, Boruto: Naruto Next Generations is set several years after the events of the original Naruto story and featuring the children of many of its key characters such as Naruto and Hinata.