With yesterday being the 68th anniversary of the D-Day landings, today marks the 68th anniversary of the moment when Hitler said "well, I'm screwed--might as well live in a bunker, get married, and kill myself". But no D-Day commemoriation would be complete without the usual armchair historian argument about whether the Allied landings were a key turning point in the war, or whether the Soviets were basically winning it anyway and we just delivered the coup de grace.
Let's solve this now, history nerds! First, it's true that the Germans had most of their efforts and casualties focused on the eastern front, and we benefitted greatly from the Soviet sacrifices. However, the Soviets benefitted a great deal from Allied efforts, including (1) the strategic bombing campaign over Germany that diverted Luftwaffe forces to home defense and stemmed German war production, (2) direct aid shipped to Russia for their own war effort, and (3) the North African, Italian, and ultimately French fronts that diverted millions of German forces away from the East. Had it not been for the Allied aid, the USSR might not have survived, or at the very least the victory would have been delayed long enough for the Germans to perfect rockets, jet aircraft, superior tanks (the Tiger and Panther), and who knows what else. The anti-Nazi coalition needed every one of its parts.
(While the Russian people certainly sacrificed and deserve credit for stopping the Germans, Stalin deserves not one shred of anything but putrid dog leavings. He's the sneaky bastard that cut a secret deal with Hitler carving up Poland in the first place, giving the Nazis the chance to overrun the rest of Europe. Historical lesson--if you're a paranoid nut, and you decide maybe it's time to start trusting people, don't make the very first person you trust in your life be Hitler.)
That said, D-Day was one of the key turning points in the European war (along with the Battle for Moscow, Stalingrad, and the Battle of Britain). Had the Allies failed--if the Germans had put enough forces in Normandy to drive them off the beaches--this would likely have delayed a landing in Western Europe for another year, with severe long term consequences (Soviets taking all of Europe? Germany making better superweapons? A separate peace?). And for all the meticulous planning of the generals, it came down to the bravery and toil of the thousands of ground troops that rushed the beaches in the face of gunfire. Even if Hitler was "almost finished" by 1944, it doesn't make a difference to a guy dodging bullets and wading through surf. Their sacrifices ultimately made the world a better place.