Socrates, I don't see how you can say that WW2 would have been won without Churchill. In the summer of 1940, with France taken out of the war, the only enemy left to Hitler was the British Empire. Churchill was the man at the top, and he is the one who said that Britain would fight on. Perhaps some other man would have done the same, but in the face of the Blitzkrieg that took out all of Western Europe, I doubt it. WIth the British Army essentially disarmed after Dunkirk, Churchill refused to settle. His courage, and the courage of all the Brits who stood behind and with him, over that fateful year, is where Hitler started to lose. He was still an ally of the USSR at that point! There was extensive trade between the two. If Britain had sought a settlement at that point, and taken a neutral or submissive stance towards the Reich, than in 1941 all of the Nazi war machine could have focused on the USSR, with no distractions in the West or the Mediterranean. The Soviets barely survived 1941, and likely would not have if the Germans could have attacked a little sooner or a little stronger.
So, yes, Churchill's presence at the head of the British Government in that pivotal time, and the way he conducted himself, were definitely essential to keeping the Third Reich from winning the war. Did the Soviets do most of the heavy lifting after 1941? Yes, with help from the other allies in material and in providing other fronts. But the fact that Germany did not win in 1940 and 1941 is a credit to Winston Churchill.