Why is it so difficult to determine which country has the best health system

Why is it so difficult to determine which country has the best health system? Describe the empirical issues related to evaluation of the systems as well as possible ways to overcome these difficulties. If you had to choose one, which country do you think has the best health system? Use course concepts to support your answer.  If you had experience with the health care system in another country, feel free to provide your perspectives as well.