"He is almost certainly a better overall programmer than I am." Hedging the claim with a lot of qualifiers. What's wrong with admitting someone is a better programmer? even giving someone else the benefit of the doubt?
Carmack might think that there are certain areas he will be better due to decades of experience. Overall programmer isn’t a bad qualifier at all, it’s actually making it sound less offhand and more honest.
2) avoid qualifiers in personal compliments (unless ironic)