War between the Soviet Union and Germany was inevitable. Had Hitler never invaded at all, it would have only been a matter of time before Stalin turned his armies west and did the same thing. The Soviet/German non-aggression pact was, 'I hate you, and you hate me, but we're not going to fight each other until... SURPRISE *****!!!"
Considering national resources, there were just too many Russian tanks and soldiers for Germany to win against the Soviet Union... ever. Speculative/alternate history is interesting though. I read a book once that speculated that if the Confederacy had won the American Civil War, we all would have united sometime in the 1950's anyways against the threat of communism. What if Hitler hadn't made all the bad choices? America had mixed feelings about Germany at the beginning of WWII, and a surprising number of Americans supported Hitler. Had he never taken up the irrational policies of ethnic cleansing and world domination there's a very good chance we would have all (Germany, US, Britain) been good friends united to fight godless, red commies, which was basically the situation in Europe immediately after WWII. After all, Hitler respected both Britain and the US for our similar culture and language.
Has anybody seen the episode on the History channel that discusses a second 'mein kampf', basically another political diary by Hitler? If it is indeed true, his intentions were pretty clear... Germany wouldn't stop fighting until they dominated the world or were destoyed. Germany under Hitler was lose/lose situation.