On krypton, kryptonians were slightly above human in their attributes. However, they didn't possess any super powers or anything. As mentioned by a poster, they lived a long time( tens of thousands of years) because they aged slower than what we as humans do, due to being kryptonian and genetic engineering.
Anyone who cells ages slow in comparison to how human cells age, would be somewhat natural healthier and more conditioned than a human being, despite not having any super abilities.
It would seem that a kryptonian(average Kryptonian) on krypton would be equivalent to an Olympic level fit human being here on earth, although they probably couldn't do the same things that an Olympic level athlete could do, since that takes special training and practice.