If Russia had to fight German alone in WW2, would it win?

Jan 2015
Front Lines of the Pig War
1. Please keep sources in English, do the viewers of Historum the courtesy, especially for a image that can't be translated by Google Chrome.
In many cases the sources aren't available in English, and I for one do appreciate seeing the Soviet sources.
Historum doesn't require English sources, only that an English translation is provided, and I think Dir has made a good-faith effort to do that.

In any event, is there a real area of disagreement here? The Soviets had a lot of tanks, but in 1941 they weren't capable of adequately defending the Soviet Union (for various reasons) or launching effective counteroffensives, so they were almost all wiped out during Barbarossa.

Back to the OPs question...

What does everyone focus on the Heer and not the Luftwaffe?

The majority of the Luftwaffe was on the Western front. That extra air power may be enough to swing the balance.
I think this is an excellent point.
If my numbers are correct, the LW has 3,500 combat aircraft in June 1941, and 2,500 of those are deployed in the East. From July 1940 to June 1941 the LW has already lost about 2,500 aircraft and pilots, 1,900 in the BoB, and another 600 in subsequent operations. (Greece, Crete, Malta, N. Africa, Channel, France, UK)

So it would be reasonable to conclude that without those 2,500 aircraft lost, the Luftwaffe could have deployed at least double the number of combat aircraft to attack the USSR than it did historically.