I think there's something to be said for controllers at a busy GA
airport as well, especially on a Saturday afternoon. Juggling 20 or more planes in the Class Delta and on the ground- some singles, some twins, some jets. Touch and gos, full stop landings, practice ILS approaches; it's amazing there aren't more midairs in that environment. Most I've worked with are very good at harnessing the chaos and keeping things flowing, while being courteous. A bad controller really sticks out in such an environment.
The large centers such as London and New York do have the benefit that most of the traffic is comparably well organized IFR. I'm not suggesting that there is an accurate comparison here- it's apples to oranges. I'm simply saying that GA
airport controllers also deserve a round of applause for managing mayhem.