Expanding in another topic,what about officers and NCO's?
My opinion:
The Germans were,IMO,the best in this area until late 1943 and early 44 when Hitler purged the general staff
A large part of the general staff was actually one of the worst aspects of the German officer corps because leading up to the war and during it it was constantly purged and honed into a passive element of Hitler's will and in the cases that it was not, it was eventually replaced by people that were more willing to work with Hitler's demands. The so-called 'Steher' (line-holders) of 1943-44 post-Kursk and of course just about everyone that rose to command OKH or were senior officers in OKW post-Blomberg/Fritsch affair. Halder and Zeitler both had some skills, but were not particularly fantastic officers in Hitler's presence. At the corps level and below the Germans had a host of great officers, while their junior officers and NCOs were probably the best in the world on average until later in 1944 due to casualties. They were probably the single reason that Germany lasted as long as they did. Certain army level officers were good as well, but once you get into the level where Hitler promoted politically 'safe' officers there are a lot problems.
In terms of the Soviets they only got better as the war went on and had a lot of excellent personnel at all levels, though even as last as 1945 there were still a bunch of poor officers in the foot infantry. Their biggest problem, besides training, was the lack of educated citizens, which crippled their NCO class, leaving it quite weak throughout the war until the end as enough people were surviving longer and longer to build up experience to make up for the lack of longer training programs and secondary education. Post-war the Soviets of course fixed all of these deficits so that by the 1950s-60s they were second to none in the tactical realm.
In terms of the Brits, their NCOs in WW2 were competent, but not extraordinary. The junior officers probably could have the same said about them, but as the war went on they all gained experience and closed the gap with the Germans entirely. Also in terms of associated nationalities like the Canadians and Aussies, they were pretty solid throughout the war. The British divisional/corps/army level was really a mixed bag, but the bad officers were largely filtered out throughout the war, leaving a solid hard core of officers at that level. The British general staff of course has had much ink spilled about it's abilities, I'll leave that up to others to parse out.
In terms of the Americans, they finished the war very strong, but took time to learn their trade and didn't have as much combat experience in Europe as their allies. Not really sure how they would have stacked up against the Soviets or Germans in their prime in a fair fight at the peak of either, were that even remotely possible, but by 1945 I wouldn't underestimate US forces' capabilities, especially in the air. Their performance in 1942-44 leaves a lot to be desired, but one critical thing you can say is they learned fast in combat and kept pushing. Probably the weakest element of their effort was their replacement system, which AFAIK was never really fixed post-war until post-Vietnam (Vietnam being a weird situation due to the conscription and tour system). Likely though the US system was adaptable to whatever pressure it had to face, so say if things went hot with the Soviets, even if they got beat up pretty bad initially they'd learn, adapt, and comeback stronger than ever.