For a tank to be good it requires a balance between armour, firepower and manuverability. I would personally give the balance to the M26 Pershing, to be honest.
The Pershing lacked the punch of the King Tiger, IS-3 and Centurion. It also lacked the armour protection. However it was the most agile.
The Centurion lacks the punch of the King Tiger and IS-3 but it's superior to the Pershing. It's armour protection is superior to the Pershing but inferior to the IS-3 and King Tiger. It was less agile than both the IS-3 and the Pershing.
The IS-3 lacked the punch of the King Tiger but was superior in armour protection to the rest. It was the second most agile, being only less than the Pershing.
The King Tiger was the strongest hitter. It lacked the armour protection of the IS-3 and was the least agile.
That's the basics.
At 3000m none of these machines could destroy the other. At 2000m the only real contender for destroying anyone else would be the King Tiger vs. the Pershing but that would still be unlikely. At 1,500m the King Tiger is in control of the situation, it would be capable of hitting all of it's opponents and destroying them. Not always in the first hit though. The IS-3 pike-nose was extremely effective at deflecting shot.
At 1000m, the King Tiger is still able to hold it's own to the front. The others armament wouldn't be capable of penertrating the King Tiger at 1000m but they would be able to cause significant shock to it's crew. However, the King Tiger could return deadly fire. It would be able to destroy a Centurion and Pershing at 1000m. And even, with luck, an IS-3.
At 400-600m (combat ranges) the IS-3 is the clear winner. It's 122mm cannon provides massive amounts of damage through concussion and other affects of massive cannon!
However, the IS-3 is cramped, it lacks optical equipment of the standard those in the West and Germany, it's still a slow firer and only contains 28 rounds.
The Centurion will most likely be firing the fastest with a light shell and good loading system. Giving the less hit a bit more damage possibility. There is such thing as armour failure.