Ground war, yes. What I don't agree is when people, and even the Russian government, like to praise that the Soviets acted almost independently. Everything they managed was achived in the joint effort. So, it's correct and very valid for the Ex-Soviet peoples praise themselfs for their achivements, but not forgoting it was part of an interconnected mutinational effort. While the West must understand the Soviet contribution as well.
It would depends in my view. Stalin would be supporting Germany with food and raw materials? Germany would conquer the USSR? In the two cases, specially in the later, certainly would be very difficult. Otherwise, Nazi Germany could be destroyed. Hitler seized much resources in the East. If didn't, the blockade and the Allied bombing, together with landings in occupied Europe probably would deal with it.
You also need to considerate that the possibility of the Western Allies defeat Nazi Germany alone is not very different than from the Soviets. Even because it's not only victory or defeat, there's also the drawn possibility. And the British proved themselfs capable of repulse the German agression in 1940.