As far as Man of Steel goes, Superman was head and shoulders above the others in the mastery of his powers. However, he was a farmboy going against skilled soldiers - something Zod himself points out. Faora took him to school in hand to hand combat, but even when Superman was facing them one on two, he still held his ground.
As for Zod's quick acclamation, he states at one point that he'd spent a lifetime learning to hone his senses and adapt to his surroundings as a soldier. He sort of mocks Clark with the "Where did you train? On a FARM?" comment. So I think its within the realm of belief that someone like Zod could master his powers quicker than Clark did.
As for the original question - yes, I think Superman should be the the most unique Kryptonian, even if he isn't the most powerful. Superman has the benefit of a lifetime of absorbing the sun's energy and has been raised with human values. That automatically makes him different than any Kryptonian that would show up on Earth. I think that Superman isn't a model just of what mankind aspires to reach - he's a model of what Krypton should aspire to reach as well.