I honestly do not think that you can rank any of the top 5 above each other these days. They all have the ability to destroy one another at combat ranges and are more than capable of projecting a presence of power on any battlefield. In tank on tank combat, it's the crew of the armour greats and the tactics as opposed to the actual combat ability of the tank.
These days a tank has to defend itself more against it's main opponent, the aircraft. The new Russian 'Black Eagle' is being kept quite tightly under-wraps but apparently has extremely sophisticated AA defence.
The Abrams is suffering under urban conditions, which would be true for all tanks. However, the lessons are learnt from sixty years ago. But it's the only option, the tank provides a basic close fire support for the infantry and projects a presence of power. They will always be required on the battlefield in any new form that they take. Armour is still a key component of warfare.
The Merkava is an impressive tank, due mainly to the combat experience Israel has had against guerilla warfare. It is has many minor improvements which are often missed out on quick reviews. One such improvement is the ball and chains hanging from the rear of the turret that, apparently, throws off shells and missiles aiming at the point between turrent and super-structure (one of the weakest parts)...if it does actually work, it's quite ingenius.
For the current kind of combat I would probably take the Merkava for the anti-insurgent kind of warfare, but for open tank on tank combat the Challenger 2.