The reality is it was not a game where one player concedes when defeat is certain. Nor a 18th Century European gentlemans war, with limited political objectives. Even if the Leningrad and Moscow transportation hubs are captured at the end of 1941, & the 150 Red Army divisions originally deployed are destroyed by December, there is still a long finishing campaign in 1942. The residual industry in the SE must be secured & the remaining Red Army damaged to the point it is no longer a strategic threat. Its probable resources equivalent to a Army group would still be required well into 1944 to prevent any residual threat from achieving anything.
A 1942 campaign with the Germans controlling Moscow and Leningrad at the start would be interesting.
The Soviets would have to choose to stick their main defense between the northern cities of Gorky, Kuibyshev and or the Caspian sea littoral cities, Baku, Astrakhan, the oil producing regions east of the Caspian, and the links to Persian gulf lend lease, the supply lines for oil up the Ural river to Uralsk and Volga river. Its a decent sized area and much of the industry was evacuated successfully. Manpower is probably the biggest weakness for the Soviets (of course there is no more civilian population of Moscow and Leningrad the Soviets have to feed).
The Germans enemy is time and distance and logistics as usual and some real choke points in the Caucasus.
I actually see the Germans being forced to keep an almost OTL army in the east, perhaps without a Stalingrad counterattack disaster. Without that I can see a couple of Panzer divisions and 4 good infantry divisions being brought back along with the Italian army in 1943, which might seriously contest an Allied landing in Sicily.