best tank
In spite of its faults, the best tank of WWII was the Panther. This is because of its combination of speed (46kmh), firepower (75mmL70 capable of penetrating 138mm of armor sloped at 30 degrees from 100 meters), and protection (80mm of sloped glacis armor and 100-110mm turret armor). The Germans probably should have concentrated upon producing the Panther and Jagdpanther, as well as tank destroyers and assault guns based on the Pz III, Pz IV, and Pz 38t chassis. The Koenigstiger and Jagdtiger should not have been produced at all.
Coming in second would be the T-34/85, which had a very good combination of speed, firepower, and protection. The Soviets probably should have produced lots of SU 100s to provide overwatch protection to the tanks. ISIIm was very good too, except for the limited ammo supply and slow rate of fire.
The Sherman comes in third, and thats only because of its reliability, numbers, and fast turret traverse and gyrostabilizer. Why the Army stuck with the 75mm for so long and cost many tank crewmen their lives is a real shame. It should have been equipped with the 76.2mm gun from 1944 on, with all 75mm Shermans retrofitted with the 76.2mm gun and turret. Shermans with the 76.2mm gun and M36 tank destroyers equipped with the 90mm would have been a good combination. Too bad the Pershing came along so late.