I'm one of those who says more seriously than joking that he was a better ex-President than President. That said, it's gotten lost just how big Camp David and the Egyptian-Israeli peace was. Israel really hasn't faced a conventional military threat since that deal.
As skilled as he was in international relations, how would the relationship with Iran have been different had he not admitted the Shah for cancer treatment? How would history have changed had the hostage rescue worked? Would the sugar-high have lasted from April to November?
He's much more significant economically, for better or worse, than is usually acknowledged. I have not seen much commentary about appointing Paul Volcker and not undercutting him as he raised interest rates. If you think price increases have been bad since 2020, 9% would have been a good year back in the late '70s. What I have seen mentioned is his initiating deregulation. Again, for better or worse. Flying became much more accessible due to deregulation without compromising safety. Deregulating transportation more generally also was net stimulative, but when later coupled with Reagan's anti-worker policies as well as Bush/Clinton liberalization of trade, it probably contributed to the hollowing out of the "rust belt."
His elevation of human rights issues contributed to the collapse of the USSR. While rhetorically Reagan was the hardball guy with Russia, elevating the original neocons like Jean Kirkpatrick, and was willing to ignore human rights abuses by anti-communists, to the anti-communist movements in Europe, the human rights pitch helped galvanize them. Carter and Brzezinski also armed the afghan mujahadeen resistance (again, for better or worse, as elements became the Taliban and as future terrorists like Bin Laden flocked to the cause).
I could make a few more political points but this is the Red Loft. More importantly, the dude's post-Presidency I think allowed him to be virtuous. His embrace of Habitat, his continuing work promoting democracy, his ambassador-without-portfolio work on hostage releases, and his work on health issues like guinea worm, weigh as much or more on his legacy as anything he did as President.