All is in the title : the challenge is to make, with a post 1953 PoD, a situation where North Korea is considered as the best part of the peninsula.
The easiest solution would be with a post-communist state in 1990's or sort of post-1989 communist state as Vietnam whereas South Korea continues to be a dictatorship.
Or, it could be sort of mega dystopia where North Korea remains mainly as OTL, but where South Korea goes wrong. I mean very wrong to be considered as worse than north.