If you look at 1990 GDP data, only four of the USSR's constituent republics had a GDP per capita over $5,000. Those were Russia, Estonia, Latvia, and Lithuania. So it shouldn't be too surprising, when we look a recent data... precisely those same countries are still the four most developed former Soviet states.

Beyond that we are stumbling into recent history. And this sub discourages discussion on recent events.

This might be a more current politics question than a historical one. What would you compare them to? It's really only the Baltics, the Balkans, and the Asian Steppe. Pretty much all of them are doing well actually. Sans Ukraine and the Caucasus for reasons involving Russia.

The Baltics might be doing better for their relations with the Nordic countries and in having small populations.

While it depends on what you are using to define the Baltics as better off, it is hard to really answer the question without getting too recent. But looking back at it the Baltics were the only part of the Russian Empire that managed to stay out of the Soviet Union during the interwar period, and their forced annexation during the Second World War and refusal to properly incorporate into the USSR likely played a part in them staying ahead. Also consider that they are relatively close to the rest of Europe, at least in comparison to the other former Soviet republics, as that may be a factor as well.