I believe, yes, the Germans could of won the war. I think the Wehrmacht is, I don’t think they made that mistake during the war, completely overrated.
Look at the facts: the Germans got within 20 miles of the Kremlin in Moscow and, if it hadn’t been for Hitler’s insistance to carry on with their assault through the winter could have easily captured it.
The Battle of Britain, could have easily been won by continuous bombings of Britain’s airfields and not on unimportant civialian targets in London and other major UK cities.
Also, the entire Nazi empire in early 1941 stretched from France to Romania, to Norway to the Balkans state. The amount of people under their rule, and mostly in the factories, was close to 1 Billion People! Even up to late 1943 and early 1944 the Wehrmacht was the best equipped, most powerful military force in the world, AND it took 3 fronts to defeat them.
It took the Russians four years to cross the same ground the Germans crossed in under a year (excluding Poland). With the Germans giving stiff-resistance at every turn.
Somehow, they could also fuel a basic defensive victory by military terms in Italy and still provide enough men to keep the Anglo-American armies pinned near the Normandy coast line for more than two months.
The Wehrmacht also was made up of several countries, comprised of a vast number of divisions, just look here: http://www.ww2incolor.com/phpBB2/viewtopic.php?t=574. And even in March 1945 the German U-Boats at sea were over 300, operating in various parts of the world including the Carribean! Also, the Luftwaffe, had it been used more properly could have seriously dampered the Allies bombing efforts.
If Russia would have been knocked out think of how much pressure the British would have to face with the Wehrmacht breathing down their neck? Think of how different Russia would be if the British did not send vital supplies.
My conclusion: If Hitler let his Generals run the war and not himself, we might now be living in a colony of the Third Reich.
In a word: yes. They could of won the war.