Why is the USA the 'greatest country in the world'?

What makes you think that (if you do)? I am not American and whenever I hear Americans saying that (usually on TV or something) I am like 'yeahhhhhh ok', I just think it seems like an overload of national pride and quite arrogant and obnoxious to believe that the USA is so much greater than everybody else. No offense to anybody out there, I genuinely want to know the reasons behind this thought. I have heard people refer to Australia as the 'lucky country' but that was normally in Lotto ads hehehe It's just that all of us other billions of people around the world like our countried too and we want to know what is so great about the USA that we should rather be there than anywhere else?