I think it is our experience. If we are really willing to learn from our experiences, that's the best teaching we get for life.
If you are really talking about educational universities, I don't believe there will be one "best". Each will have its own flaws which only insiders know or you will know once you enter inside!
I should say any one university amid top 4 to 5 universities in the world should be good enough for anyone to choose, if one is really so particular about the 'top".