Certainly great beer can come from anywhere. But just for fun, I'll postulate that the best beers, or at least the most creative brewers, can be found in countries in which brewers have the most freedom, or the least tradition.
There are some wonderful beers in Germany, for example, but the stylistic range is limited by tradition, and even by law in some cases if I understand corrrectly. Ireland has some great ones, but they're mostly traditional stouts and Irish reds. Contrast this to the Belgian or US brewer whose only limit is his/her imagination. The numbers of unique and new beers is phenomenal in these countries, and for me, they're often the best.