They'd still forced into using the unplanned-for Plan B which they had to concoct bc the Soviets had destroyed Plan A at the Battle of Moscow in Dec, 1941.
Hitler was adamant that air power be used physically destroy Moscow including its entire population.
He thought destroying Moscow would mean the immediate unconditional surrender of the USSR.
But by the time of the Battle of Stalingrad in late 1942-early 43, the Soviet war machine was in full cry with its factories at least equaling Germany's production of materiel, and the Red Army was quickly bringing to the Eastern Front many divisions of battle-proven Siberian forces.
Red Army general Zhukov had used them a double encirclement counter-offensive that he made famous to destroy a major Imperial Japanese Army division on the USSR-Manchurian [Chinese] border in 1938 to permanently terminate the Japanese threat to the USSR. [He used that same counter-offensive maneuver more famously @ Staingrad.]
And the Soviets were receiving large amts of aid from the US' Lend-Lease program in the form of weapons, ammo, fuel, raw material and vehicles.
By the war's end, 2/3's of the Red Army's trucks were made in the US and many were fueled by the US.
The USSR received 2,000 locomotives from the US for its war effort.
Even in the late 1930's Hitler and the Japanese knew they were losing the arms race.
So if by some quirk the Nazis won at Stalingrad, they still would have faced the impossible task of a greatly out-produced industrial base attempting to supply a 1.5 million man army in the notorious Russian winter over a 1,500 mile-long front over 1,000 miles from Germany.
The Wehrmacht's, and Nazi Germany's fate would have been the same.
Maybe worse bc they would have fought an impossible losing fight for a longer period.
Stalingrad was much more decisive; Moscow was a lost battle that seriously disrupted Nazi war strategy.
But at Stalingrad the Soviets physically destroyed the German's flagship 6th Army and 4th Panzer Division and permanently broke their morale.
Of the 230,000 German troops in the 6th and in the 4th Panzer, 5,000 lived to return to Germany.
Zhukov went to Germany as commander of the First Belorussian front in the Battle of Berlin, May, 1945.
He told his troops "We will extract brutal revenge here for what the Germans did in Russia."
He was promoted to Marshal of the Red Army and appointed commander of the post-war Soviet Occupation Zone in Germany.
General Dwight Eisehower was a great admirer of him and they toured the USSR together after the German surrender.