It goes without saying that the Rickest Rick would have the Mortiest Morty.
Come to think of it, Rick didn't exactly imply our Morty is the Mortiest Morty. It comes across as Rick complimenting Morty C-137 in a way that doesn't step on his own ego, but it can also be seen as a nod to the theory. Or, actually, no. That's retarded.
Maybe evil Morty is the Rickest Morty? Mortiest Morty doesn't sound like a good thing.