Against that, a conservative might properly fault Churchill for playing a role in the British progressive reforms that occurred at the same time there as they occurred in the United States. I am not sure how I would grade Churchill for his association with Lloyd George and his leading role in so many British laws that ameliorated the Dickensian effects of the Industrial Revolution. I could defend Churchill by saying that he was engaged in a society fixed by class which cried out for some sort of amelioration for the underclass and he provided relief by way of child labor laws etc. Moreover, a conservative might take note that the British constitution presents no real inhibition to socialism to the degree that the American Constitution does nor was it part of the English culture. Nevertheless, Churchill spoke out against socialism and communism his whole career. At the end of the day I am not enthusiastic about Churchill's role at that time but he certainly did not support but explicitly opposed the socialism of Clement Atlee which came two generations later after World War II.
I elevate Churchill above the three you mentioned because he was a Renaissance man, an author of matchless ability and staggering output, a wartime leader, an active soldier, a statesman, a bulwark against Nazi-ism as well as against communism. Reagan was a great man and so was Thatcher also great but they did not possess the multi-dimensional talents of Churchill. I do not believe that any one of the three could match his intellect for sheer candlepower of IQ. Reagan and Thatcher were good, perhaps great orators, but Churchill "mobilized the English language and hurled it into battle," as he was described to have done by Kennedy, no doubt ironically using Ted Sorenson's words.
Churchill stands above them for his durability, he dominated history from 1900 to the 1950s whereas Thatcher and Reagan had influence for much shorter terms. Churchill bridged history from a cavalry charge wielding a saber to the atomic age and he contributed mightily in every decade.
If one gives credit to Reagan Thatcher and John Paul for bringing down communism certainly equal or greater credit should go to Churchill for recognizing its danger in 1919, his opposition to it throughout his life, his alerting the world to it in 1947 at Fulton Missouri with the Iron Curtain Speech, his attempts, which were undercut by Roosevelt to head off Soviet domination of Eastern Europe which he foresaw and Roosevelt did not, mark Churchill as the lone statesman of the era who saw at least by the end of the war the true nature of Joseph Stalin.
Finally it was not just that Churchill was a leader in World War II, it was that he saw the strategy which ultimately brought victory, mobilized the world to engage against the heaviest odds, saw his nation saved and victorious, provided the vision and the language by which the free world would prevail. He virtually alone foresaw the Nazi threat and he had the vision to see how it could be defeated and the courage and the talents to bring about.
