AS much as I despise the name sake of this tank, I would argue that the IS-2 (Stalin-2) was the best heavy tank of the war.
http://www.wargaming.net/tanks/MODELS/js2.htm
120mm frontal sloped frontal armor
122mm high velocity cannon.
max speed 37km/h
hieght of 2.73 meters.
It ate Tigers for lunch. King Tigers were their equals, but the Soviet design was more reliable adn produced in larger numbers.
Of course tactics count. In the 1967 War, the Israelis used upgraded Shermans against IS-3's and won.
A lot had to do with the tactics used. The Germans were masters. They were fighting with "Divisions" that had a tank strenght of 35 tanks sometimes.