Was WWII worth it?

Was WWII worth it? Pat Buchanan makes a compelling argument about WWII, whether or not it was worth the death and destruction. Buchanan argues that if the goal of WWII was to liberate the Eastern European governments then one must consider WWII a failure because the allies did not achieve these goals. Buchanan argues that these countries simply transferred from one brutal regime to another. He certainly does have a point, there were around 50 million people killed by WWII and none of those eastern nations were liberated. Buchanan main argument is that communism was worse than the Nazis, he said:
“Where Hitler killed his millions, Stalin, Mao, Ho Chi Minh, Pol Pot and Castro murdered their tens of millions.”
The problem with this logic is that it assumes that Pot, Stalin, Minh, Mao and Castro would not have gained power if the Nazi’s had been allowed to stay in power. Stalin was already the controlling Russia, certainly Buchanan cannot be implying Stalin would have been a peaceful ruler had Hitler remained in power.
It seems more possible to me that the Germans would have taken the lead much the way the Soviet Union did during the cold war. If the Soviets had an ally as strong as Nazi Germany, we might not have won the cold war. Furthermore, the cold war might have become the hot war. Stalin and Hitler did have a pact before the war. If Churchill and FDR had not taken out the Germans when they did, the relationship between Hitler and Stalin might have blossomed into a real alliance, that’s scary.