London is the best! Easy public transport, theater scene, free museums, great parks, great sights.
Singapore is a close second. It's like Asia's London. It has broadway / west end shows too like Wicked and Lion King. It has a great Zoo and Botanic Garden. It even has a Safari (at night)
Hong Kong is cool too but Singapore clearly beat it IMO. The big minus in HK is taxis from one region may refuse to take you to other regions.
The worst i've been too is Shen Zhen. Hong Kong's neighbour but like day and night! No wonder Hongkongers hate mainland Chinese.