You forgot Cuba and Haiti - and that is more than just a minor omission. You see, all the countries you mentioned, Korea, Germany etc. were buffer zones surrounding Soviet/Chine controlled land-mass. It was in the best US imperial interests that these bfeer zones stayed economically healthy on the pain of rebellion. So while the Americans pumped money to West Germany under the Marshall plans, tho Soviets pretty much looted the East of its industrial infrastructure. The East and Weste Germany were not exactly socially equivalent either, the East was the stronghols of the junkers, while the West was more urban and industrial. But that is a mionor point.
Cuba, on the other hand, could be seen as a buffer zone in reverse, and oupost of the Soviet imperial intersts if you will. And it prospered comparatively to the neighboring countries of similar size and social structure.
That pattern suggests that superpower geopolitics mattered, perhaps even more than ideological declarations and styles of the respectives regimes.
Moreover, if you look at the trajectory of economic development, you will see that the developing countries that adoptyed central planning and land reform initially scored much better than the countries that did not adopet these measures. Land reform is crucial because it breaks the backbone of the landed aristorcacy that is _the_ major known brake on economic development. Central planning, in turn, optimizes economic preformance mainly by minimizing transaction costs (cf. Williamson's _Markets and Hierarchies_ for a theoretical argument), by creating the central banking system where none existed necessary to finance the industrial project (cf. Alexander Gerschenkron, _Economic Backwardness ina Historical perspective_), and also curbs inflationary pressures that hike in demand would inevitably increase.
So when you compare the land of general secretaries to other lands, you need to say in which period of time, for otherwise you will be comparing apples and oranges.
Finally, you need to specify what objectives the general secretaries tried to accomplish. If you take the PR spiel on the both sides of the iron curtain for the face value and believe that it was "exporting communism" - then well... you can jump on the banwagon and celebrate your victory in the cold war. If, on the other hand, one believes (as I do) that the main objective of the general secretaries was to overcome backwardness, speed up their economic development, and catch up with the developed countries, then I suggest you congratulate them. For their have not only been tremendously successful in that task, but also very open minded about their own power and using to the benefit of their countries. Intitially, when the command economy offered a clear economic benefit, their held steadfastly to it. when the initial economic growth started slowing down, they started implementing reforms and gradually giving up their own power.