How to judge a central bank?

The Bank of Canada is often credited for having fared better than the US Fed in handling the Great Recession. In fact, Mark Carney was handed the Bank of England governorship mainly because of the Bank of Canada's success.

But you can't see that success when you look at nominal GDP (cc Scott Sumner):

On the other hand, Australia has done very well:

Australia hasn't had a recession in 20 years. 20 years! But like Canada, Australia says it targets inflation, and certainly not nominal GDP. Yet Australia is faring much better.

Very peculiar. Maybe we're overlooking something.