It was a Bush related joke. But regarding what you wrote, Ukraine prospering doesn't seem very likely, it's much more corrupt than even Russia. Their GDP per capita is a third of Russia's, despite also having a wealth of raw materials.

So that's not the issue. The Baltic states have prospered, and joined Nato for that matter.

The problem is that Ukraine is a huge country with a pretty large population, plus it has very deep historical ties with Russia, so it's probably a bit of that too, losing ones brother to the enemy would hurt.