In Hong Kong, which IMHO is the most beautiful city in the world, you can stay 3 or 4 days, it is not a big big city, but there are plenty of restaurants, Victoria Peak, The Harbour, Shopping, etc.
Tokyo is also wonderful, you can spend more time there since is a big city. Many good restaurants, shops, palaces, day trips (say Mt. Fuji). I would say 7 or 8 days.
MDE: First airport in the Americas visited by the A380!