It really depends on what sort of beer you are referring to, but the 2014 winner of the best beer went to "Haacht Brewery" in Belgium. So therefore it would seem that the best beer in the world is brewed in Belgium!
There are annual awards for beer (as you will see from my reference to the 2014 winner above) and these guys take their beer pretty seriously.
Each year they dish out awards for the best dark beer, pale beer, sour beer (doesn't sound too nice to me!), flavoured beer, wheat beer, specialty beer etc.
You can view the whole list on http://www.worldbeerawards.com/2014/ and then having fun traveling around the globe deciding whether you agree with their findings! Better still, maybe you could become a judge, now wouldn't that be a satisfying career? :-)
If you do explore the world of beer a little deeper, you'll probably find that there's no one country that dominates the craft of beer making - from the US to Bavaria there are some fine beverages being made all around the world.
It really comes down to the skill of the individual brewery, and your personal preference!