One US ... ;) Although probably 7 out of the top 10 busiest airports are US ...
Things like 'favourite this' or 'best that' are best not polled as people will usually have their own which the poller could never think of

My personal favourite would at this moment be Courchevel - a high resort in the french alps with a short sloped runway ...
Big airports would have to be the busiest - Atlanta

& give me any helipad on any building any day!! I can't get enough of those landing spots .. :D
Simplicity is the ultimate sophistication. – Leonardo da Vinci