Superboy Prime obviously has an incredibly high average, taking it to Guardians, re-arranging the universe (over time), taking it to the GL Corps, throwing the remnants of the Anti Monitor galaxies away, etc.
But he's got his low showings to. He's had trouble, and had blood drawn by, Superboy (Kon El/Conner).
Putting him above Darkseid - who has such a long and storied history, who has been a part of CRAZY feats like creating universes or causing the destruction of the multiverse by his very entrance, feels kind of unreasonable.
Even if you leave off from the Final Crisis stuff, since that was a retcon of his 'true nature', even if you just go with all the non-Final Crisis stuff, he's still created universes (in Seven Soldiers, in Batman), he's still casually imprisoned the entire Legion of Superheroes (in Foundations), he's still destroyed Mordru and a high level Time Trapper 'stand in' (in GDS), he's still no-sold Lobo, etc.
His average is much more variable, but putting a relative flash in the pan like Superboy Prime above him is unfounded, as far as I'm concerned.