When someone says, "Gibson banjos or Martin guitars are the best in the world", the obvious problem is, no one can say that as a fact, only as an opinion, because, no one has ever played every banjo or guitar in the world.
It's like McCain saying that America is the greatest country in the world; I've never heard a European say that. It's a matter of opinion, no more.

For many years the Cadillac company had an advertising claim that Cadillac was the "Standard of the world." Sounds good, but what does it mean?