It really depends upon the experts you want to use as a reference.
For German armour, probably the best all around tank was the Panther (Panzer V), it had a great high velocity gun, good gun sites, good speed, excellent armour protection and a well sloped glacis plate. Except for the early production, it did not have the reliability problems and poor power of the tigers. Perhaps the best anti- tank armour was the Jagd -Panther with it’s simple design, lethal 88 and super thick well sloped armour..
For the Allies, the tanks equipped the the 17 pounder were the only ones that were able to approach the Germans in gun performance and none were very well armoured, except the M4A3E2 Jumbo. Note: the 90 MM gun's muzzle velocity and penetrating power was not as good as the 17 pounder. The exception, (aren't there always exceptions?) being the Super Pershing which was experimental and bagged only 1 Tiger II. The Pershing was the tank that the US should have had several years before, instead of continuing with the obsolete Sherman. According to one US source I read, you can thank General Patton for that.
Despite this, the reliability, speed and fast turret turn rate of US tanks , especially the tank destroyers made them formidable opponents using shoot & scoot tactics.
It's pretty hard not to include the russian T34/85 as one of the all around best tanks of the war. Fast, well sloped armour, excellent gun , diesel power, very reliable, easy to use, and able to go where most tanks feared to tread - because of it's wide track and low ground pressure. This tank cause a revolution in German tank design resulting in tanks like the Panther & Tiger.
The Centurion deserves some mention because it borrows heavily from T34/85 & Panther design and is one of the most long lived WWII tank designs.
By any post war measure, the 2 most successful WWII designs to come out of WWII and have cuurency long after, are the T34/85 and the Centurion. The Centurion proved it's battle worth quite readily in Vietnam & Korea where it proved to be much hardier than the Patton or T34/85. In the hands of the Israelis, it proved to be lethal.
Anyway, that my 2 cents worth.
By the way, the Russian JSIII put the fear of God into everyone. Here is a quote:
On September 7th 1945, the allied nations were staggered by Russia's disclosure of their JS-3 heavy tank at a victory parade in Berlin. Although coded a JS (Josef Stalin) tank, it had a totally different appearance from its preceding models. The one-piece cast turret had a simple flattened hemispherical shape. The maximum thickness of the turret armor reached 250mm. The front hull was constructed by welding three 120mm thick armor plates, forming a shape like a ship's bow. The main armament used the same L/43 122mm gun as the JS-2. The 520 horsepower diesel engine provided 40km/h of maximum speed.
Here is the URL to give you an idea of the killing ability and distance of some WWII opponents:
http://homepage.tinet.ie/~nightingale/killing.html
Cheers,
HD