Algy
Ignore HD - he's retired and so must be a grumpy old git, it's expected of him
Seriously though, the query is far too broad based so as to be meaningless. What is meant by 'best' ?? Overall, in specific areas, or just subjectively ?? And how do we measure it ? What's the control sample ? What's the survey group and makeup ? And so on and so forth.
If it's things like delays you want to measure, then for Europe at least, Eurocontrol publish tables. But these are just raw data, there is no account of airspace complexity, constraints, etc. Or if it's cost, then there is a similar thing. But again, no account of charging regimes, government 'assistance', cross subsidies, etc. Or if it's aircraft moved per staff member ....... the list goes on. None conclusively prove anything as you often compare apples with oranges and there is little info on what weighting is given to any assumptions being made.
If you want to know who is best in class, then you need to provide a lot of data on what you want to measure to provide anything meaningful.
Regards
PR