The Soviet Union was like a table sitting on one leg. It's system WAS unsustainable. Hell George Kennan knew this back in the 40s.
However, Reagan was the president that had the guts to challenge the notion of containment, and instead wanted to actively put pressure on the Soviets.
I think his foreign policy was solid. The only thing idiotic was the Strategic Defense Initiative, which threatened the security of MAD which had sustained the Cold War peace for so long.