Since the start of the Boruto: Two Blue Vortex manga, the series has showcased the results of the titular character's training during the time skip. These instances have seen the protagonist use the Fourth Hokage Minato Namikaze's Flying Raijin Jutsu.
However, that isn't the only new jutsu in the protagonist's arsenal, as he has also showcased his newly created jutsu Rasengan Uzuhiko. While the manga has yet to unveil the Jutsu's origin, i.e., how the protagonist came across the idea and put it to work, the jutsu's nature suggests that the protagonist may have already surpassed his grandfather.
Disclaimer: This article contains Boruto: Two Blue Vortex manga spoilers.
Boruto's Rasengan Uzuhiko surpasses Minato's Rasengan

While several jutsu have branched out from Rasengan, the primary jutsu itself was created by the late Fourth Hokage Minato Namikaze. Minato created the jutsu to help his lover, Kushina Uzumaki. Being a Jichuriki, it was inevitable that Kushina would be deployed to fight strong opponents. Hence, after observing a tailed beast using Beast Ball, Minato created the jutsu so that Kushina could use it.
While manga or anime never revealed if Kushina inherited the jutsu, overas passed on to other Shibobi with time. Some users were Naruto Uzumaki, Jiraiya, Kakashi Hatake, Konohamaru Sarutobi, etc. While the number of users was quite limited, each Shinobi created an alternate version of the jutsu, the latest one of which is Boruto's Rasengan Uzuhiko.

Rasengan Uzuhiko is based on the main jutsu. Hence, earlier, one may have theorized that the new jutsu only observed a change in its chakra nature similar to other Rasengan variants. However, the Rasengan Uzuhiko is entirely different from others.
This is because, unlike the main jutsu and its alternatives, Rasengan Uzuhiko does not derive its energy from the user or any external chakra that is channeled within the user's body, like Sage Mode or Tailed Beast Mode. Instead, Rasengan Uzuhiko channels external energy directly.

As explained by the protagonist in the manga, Rasengan Uzuhiko uses the energy of the centrifugal force accompanying a planet's rotation and orbit (planet's chakra). The effects of the same force a target to undergo the incomprehensible forces exerted upon a planet during its movements.
When the Rasengan Uzuhiko is used at a minimal output, the forces deem the target unable to maintain balance and fall to the floor. However, when the jutsu is used even close to its maximum output, it can destroy its target's body.

Considering the sheer size of a planet, the jutsu's chakra is effectively unlimited. Thus, if Boruto were to use his Rasengan Uzuhiko at its Maximum Output, the power generated by the same could be unlimited.
Therefore, with the creation of Rasengan Uzuhiko, Boruto may have surpassed his grandfather in creating a Rasengan Jutsu, as the Uzuhiko could quite possibly be the strongest jutsu in the franchise.
Related Links
- What does Uzuhiko mean? The mythology behind the new Rasengan, explored
- Rasengan Uzuhiko might be the second Kekkei Touta in the entire franchise
- Why Minato with Sharingan in Naruto could have changed the Narutoverse, explored