To define the best tank in the world you have to first look at a few factors.
First factor:What is the tank being used for?
Second factor: Is the tank going to be as useful in one situation in comparison to another tank?
Factors explained
Countries usually select or build tanks which are specific to their needs. The Merkava is a heavy transport tank, it can carry 6 soldiers internally inside the tank. No other tank can act in this role. If you were to give for example an M1 abrams to Israel to use in urban environments it would not perform as well as a Merkava in an urban environment. It can't carry troops safely into urban environments, so it is not suited for that role. So a traditional tank is not suited or to be frank, not the best tank in the world for Israel.
This is where you come to the conclusion, who is this tank for? Every country in the world has needs and to attain those needs tanks have to have certain requirements.
The Leopard 2 does not have a rifled barrel, only the Challenger 2. Smooth bore cannons are perceived to be much better considering that they offer a higher calibre which equals a bigger punch. Along with this there are more rounds of ammunition types with smooth bore in comparison to rounds that can be used in rifled barrels. If you try and counter and say that smooth bore cannons are less accurate, then you are in correct again. The margin of accuracy is so little it doesn't mean a thing. Take a look at how the M1 Abram tanks obliterated targets in large numbers in the first and second Gulf War. At this point, you are thinking, what about the Challenger 1 and the fact it has the record for the longest tank on tank kill in combat. Other tanks in training have scored hits in similar range against other static vehicles similar to the situation with the Challenger 1 and long range kill. This is no special feat as smooth bore weaponry can also do the same with a bigger punch. - Especially with today's gun stabilisation and digital systems which help improve accuracy which have been upgraded over the years, improving the technology which the Challenger 1 had.
In conclusion, it is dependant on the country in question that acquires the tank that decides whether it fits the role of being a tank that is suited for that countries terrain, mission and goal.
Opinions will always vary, and are dependent upon the test conditions provided.
challenger 2 is the best tank in the world
No, doubt its one of the best tanks in the world. And demand for Al-Khalid tank in the world is increasing. Its completely manufactured in Pakistan.
it is an M1A1 Abram
Yes. It was the best in the world.
3 Russian 2 UK 1 USA
The KV-2 is the best tank.
The biggest tank in the world would probably be the US M1A2 Abrams main battle tank.
It is the SU-18 on SPG mode, click shift
French Renault model 1917. The US Army adapted the Renault as their first tank; and produced them under license.
The most advanced tank in the world is the M1 Abrams Battle tank that is for the U.S.
the best tank of all time will need to be the the T/34 85
* IS tank, a Soviet heavy tank in World War II