I agree that it would be foolish to state the war was lost from the outset. I also agree that many people assert this theory with the benefit of hindsight and a desire to make the German Army look bad. Granted it has been a bit overated by some historians, but much is being done to undermine its quality simply due to bias. There were definate obstacles that were not taken seriously or were overlooked as a whole; terrain, logistics, war production, etc. These have been mentioned above and need no further mention. However, despite these mistakes and pitfalls, I fell the Germans still came quite close to victory at several points during the war on the Eastern Front. To me this is impressive. Obviously improvising they still managed to come that close and hang around as long as they did. If it was as disastrous as many say it was, in my mind the invasion would have collapsed and limped back to Germany much sooner than 1943. It's obvious, but had anyone in the military actually been able to do thier job and plan the bloody invasion, or advise Hitler to the dangers of it, the Germans would have won quite easily. If I might add to FramerT's comment about North Africa or Russia, not both, I would sight leaving England in your rear unconquered as being a deadly mistake adding to the failure in Russia.

__________________
Cheers,
Daniel