This thread reminds me A LOT of the infamous Marvel/DC "Who is stronger?" threads in off topic.
Anyway...
Let's put it this way:
Rosalina is "Galactus" type of power.
Shulk is sort of "Franklin Richards" level.
Kirby on the other hand truely is the "One-Above-All".
As I stated before: He accidentally inhaled "Existence".
Therefor he IS omnipresent, omnipotent, omniscient and omniversal.
Even though he might not even recognize it.
plus: Others ride Harleys. He rides a fucking star.
He's also 8 inches tall...