Japan - bland
Singapore - boring after 2 days
Malaysia - my least favourite country on earth - degraded environment, nothing works
China - fascinating but difficult and unfriendly
Hong Kong - okay for a few days
If budget stretches, go to Europe. The world's best holiday of 10-14 days is a tour of northern Italy - Milan, Como, Venice, Florence, Pisa etc. Next best: Provence/Cote d'Azur. Next best: Andalucia. Next best: Switzerland. Asia has nothing to touch these places.