lets see
Infantry: Germany
Best troops, best weapons,
Armour: Germany
Great tanks, short on mechanical reliability though
Air: US
american planes are of great quality, thats for sure
Japanese pilots often used up all their ammo and still fail to destroy a F6F
Navy: Japan
The best battleships, and the best carriers
Morale: Japan
Most determined troops in the war
Propaganda: Germany
So successful that there is a Goebbels' mass media in China
Troop numbers: Soviet & US
Well the soviet union was able to field the most troops, of course US numbers for the navy
Logistics:US
Well the US was able to supply many allied countries with equipment and supplies
Secret weapons:
this is a tough one
Germany had rockets, Japan had bio weapons, Italy had the human torpedo
but still, America had NUKES