Hi! I find it really funny, how people think this or that in History is impossible, would never fly, etc. just because OTL it did happen a specific way. What some persons overlook is the fact that even OTL many historic events were knife´s edge and could have gone the other way or even a third or fourth one!
Moscow (and Stalin) falling in 41 would be a major blow to the SU, it was THE hub of the SU, traffic, industry, you name it. With the capital fallen and a war of succession in the government, Germany has the chance to mop up the eastern front in 42. Unlike 1812, as some here believe, the Sowjets don´t have the option to burn anything down before the Heer arrives, since back in Napi´s time Moscow was not that of the importance in 1941. To stay in the fight, the Sowjets have to take back Moscow halfway intact. If the Heer can hold the city against the inevitable counter attack in early 42, it´s mostly over in the east. Without Moscow, the Sowjets are seriously hindered in transportation of anything. Some OTL offensives will not happen TTL, since the hub making it possible, is in German hands TTL.
If Germany supplies Army Group Center by air and rail in Moscow, even if it will be barely enough due to the distances involved (it will get easier a bit by the installations in Moscow), they can hold out.
By end of 42, early 43, there will be negotiations. And contrary to what some here might think, Hitler will take that peace! TTL Hitler is still a megalomaniac, but he never suffered the Trauma Stalingrad gave him OTL and the fighting power of the US will make him hear more to some Generals and more, Hitler got what he wanted in the first place: the East. TTL Hitler will be more reasonable, since he never got the setbacks that made him the idiot of after Stalingard OTL.
Oh, and Good Bye to the big, honking armies of the western allies coming to the rescue with atomic bombs and all! With the eastern front gone, a painful go in the Pacific and in 42/43 the bomb is still some time in the future and not an instant war-winner, it is far more likely that the war between Hitler and the western allies will become a Cold War.
Without 2/3 of the Heer fighting Russia, there will be no successful landing in France. And that the West will fight until the bomb is ready is a hind sight myth! In 1943 there was no assurance the A-bomb will be a weapon that can be used! The development stage was still too early to say that at that time or if the development will be producing more than hot air.
With Germany able to move the majority of her forces west, she can counter any landing and inflict far worse damage on the bombing campaign.
It is far more likely that there will be a grudging cease-fire and a Cold War afterward.
See CalBear's "The Anglo/American-Nazi War" for what the aftermath of a Germany successful in the East would look like. Round 2 happens in the 50s, with Germany on the wrong end of a 3-1 disparity in industrial strength and delusional leadership. Guess what happens.
CalBear has even admitted that the premise is more or less ASB.
As to the OP, I think the fall of Moscow would hurt the Soviets greatly, but it wouldn't mean an instant peace. I don't think Stalin would stay in Moscow if it looked like it was going to fall. That means that the Soviet leadership still has one man on top who is giving orders and serving as a rallying point. The Soviets will hang on, since they have the Urals industry and rapidly growing amounts of American Lend-Lease. They will be significantly weaker by the end of the war, but they will win in the end.
Also, I think the imminent fall of Moscow will result in British and American attempts to draw strength from the Eastern Front with attacks around the periphery of Nazi Europe. I think the amphibious attacks will likely end in bloody failures, as seen in Dieppe. There will likely be attacks in Africa, which could have more success.