Germany was the greatest war-waging nation. She brought 5 great nations to their knees but as soon as the Americans decided to enter fully she was destined to fall. As far as war-waging goes I got to hand it to Nazi-Germany. As for America as the great liberator, I'd say the combination of Britain and America was what sealed the deal.They were the financial powerhouses, lending money to other countries, and battled well. Soviet also, obviously, played a huge part, with their endless number of soldiers. But anyway, my point, if it had been a battle between Nazi Germany and USA, The Nazis would have won. The only reason they didn't is because they had shit allies and had to battle Britain, Soviet, France, smaller countries with resistance movements, basically they took the World head on! Not an easy task but they almost freaking did it.
First of all, in terms of efficientcy, Japan was probably more of a power-house.
Germany was in all respects, but what nations did it take down?
Poland - Polish Army rode into battle with horses vs. Panzers, and the overall Blitzkrieg.
France - Well, there is an old joke that says, "Why are the streets of Paris lined with trees? The Nazis like to march in the shade." That says enough.
Nederland - Meh, they did not really do anything, pretty much stuck to neutrality and what not.
Sweden - Same as above.
Denmark - Same.
Belgium - Took all of 3 soldiers and a gay-guy named Hans to take over Belgium because they ate their waffles and declared it West-German-Non-Existent-Country, little known fact.
German name for Austria is Oestreich, which means the Eastern Reich, so they weren't anything special. Swiss, they made chocolate the whole war and took a lot of Jewish money into their banks which the Nazis stole, so they actually profitted off the macabre of massacre.
And.....what USSR/Russian Empire?

The Russians were the ones that won WWII, and if the Germans had entered the war 3 months later, they might have taken a lot more of Russian than they did. The battle of Kursk and Stalingrad would have been different. The Germans entered the war in June of '39 I believe, which shows why the Germans had a rough time in the USSR, they were equipped with Summer Uniforms...
Plus Russia won the war on the Eastern Front by true attrition, the Russian winter waso cold the metal of the Mausers and the 98's and the MP 40's just became britle and broke after a couple of rounds. The Germans had to start fired under their trucks to prevent the oil in the crank cases from freezing....that or, in the case of the Tiger I and Panzers, keep them running all the time. This was a problem because as good as the Tiger was, she guzzled Deisel and even in normal weather had to be started up every 2 or 3 hours just to keep the machine from breaking down. The Tiger's fuel system leaked all over the place anyway, so imagine it being -25C or so and have freezing Deisel leaking all over the inside of your tank. So the Germans were using fuel faster than they could ship it out to the Eastern Front just because they had to keep the fookin' tanks and Opel Blitzs running 24/7. Which also puts a lot of strain on the engine in general. So the Russians owned not only because of this, but I don't know if you have looked recently at the former Soviet Empire, but the thing was FUCKING HUGE. We are talking about a people who decided, well, we are tired of having our tank factory bombed, SO LET'S PICK IT UP AND MOVE THE WHOLE FACTORY BEHIND THE URALS. This allowed them to produce almost as many T-34's as we did gasoline powered Shermans, which neared 400,000. Do you think the Germans had this ability? To move the Berlin Messerschmitt plant? Where the fuck would they move it?
So, all of these things, plus the Russians were battle hardened for centuries. Burning Moscow when Napoleon tried to come in...so he said fuck that. Plus the Russians are a very nationalistic people by nature, much like the Germans, but not near the extent based primarily on the larger nation, more population. The Soviet War Machine won WWII.