Such is the advance of modern production techniques used in wine making I would personally say; the southern hemisphere.
By that I am referring to Australia, New Zealand, South Africa etc. All these countries rate highly. However, there are other countries that are challenging the currently accepted main producers.
Wine producing countries such as South America, Argentina, Chile, Bolivia, Peru have really developed well and all produce some fantastic wines.
Other countries to watch closely are those in the far east such as China and Vietnam which are beginning to produce some amazing wines using western root stock and modern production techniques.
To end, I’d just like to add that it all boils down to taste. When you have been drinking wines for a few years, you will soon be able to recognise the different tastes and styles of wines from any particular country and you will come to know what you like and don’t like and which country your preferred wines come from.