Russia > Iran > North Korea (through forceful annexation by South Korea albeit) > China
Russia is the one that's closest to Western values. It's the only one that has experimented some form of democracy and freedom at some point in its history (right the fall of the Russian Empire and in the years following the fall of the USSR).
Iran, on the other hand, jumped straight from having a CIA-backed monarchy to having a totalitarian ultra-religious state. Even the "moderates" in Iran are hardly moderate by Western standards, since they advocate for Islamism but not for expansionistic campaigns.
The North Korean regime probably won't become democratic any time soon, but if it did, it would be due in a state of utter crisis, totally lacking food, supplies, and other goods. North Korea wouldn't become a true democracy, unless forced to by South Korea. At worst, it could devolve into Somalia-style anarchy if not quickly conquered and put into submission by South Korea.
China is the one that seems the least likely to accept democracy by the very nature of Chinese collectivism, which is inherent to Chinese culture. Whenever great dynasties collapsed in China, the resultant power vacuum more often than not led to various warlords fighting amongst themselves for control of the country, with the victor becoming the new Chinese emperor. To put it in another way, a country as massive, as heavily populated as China is unlikely to see the emergence of different opinions being allowed to flourish and compete against one another. Individuals may disagree with government decisions, but dissenting political blocks would simply be quashed by force. Anything else would lead to millions of different opinions competing amongst each other and people being unwilling to cooperate with each other, which is what happens in countries like Brazil, India, and Mexico.
