Well, Hitler's decision to leave the USSR alone was based on a number of factors that could easily have gone a different way. Most historians agree it was the work of people such as Haushofer, working their way into the Nazi inner circle, who helped change the focus of the Nazi regime from Lebensraum in the East to domination in the West, as well as control of Africa. The key was probably to get Hitler's mania focused on the French, as traitors of Germanic civlization, and convincing him that the Russians, being an inferior race, would eventually destroy their own civiliazation if left to their own devices (which is exactly what happened several decades later, although it had much more to do with Communism than racial theory. In any event, it was significant.
The new plan's culmination in the annexation of the Low Countries, Denmark, and the northern half of France changed the map of Europe as drastically as Hitler's original plans would have. The plight of the Africans in the "German Colonial Zone" was at least as horrifying as what would have happened to the Ukraines, Byleorussians, and Russians if Hitler had invaded the USSR.
But as for what would have happened then? Judging by the Soviet Army's performance in Finland at the time when this could have taken place-ie, before atom bombs and MAD entered the picture-the Wehrmacht would have crushed Stalin's Empire with ease. The main difference in the ATL to OTL would be that Hitler would probably then concentrate on his one gigantic landmass as his base of power, rather than several large plots of land on three continents, connected by a formidable Kriegsmarine. The control of Russia would also have prevented the long Civil War in China, as Mao Zedong would have lost much earlier, and Chiang Kai-shek would have taken control long before 1956.
The conclusion would have been very different in a two-sided Cold War, as opposed to our three-sided one. In retrospect, of course, it might not have been the Nazi's best move anyway-in the end, Hitler got his Eastern living space, when the Soviet Union fell apart and the weakened, unstable Russian Union couldn't stop the Wehrmacht from taking Byelorussia, Ukraine, and the Baltics. The very fact that the current Fuhrer has set up another round of vicious pogroms against his new slavic subjects (all the while denying it) just goes to show that the essential nature of the regime never changed-and the dream of Lebensraum, while restrained by alternate theories and common sense argument back in the Thirties, never faded away.