准确答案如下:
1.Beijingislarger/biggerthananyothercityinChina.
Beijingislarger/biggerthantheothercitiesinChina.
Beijingislarger/biggerthananyoftheothercitiesinChina.
Beijingisbigger/largerthanallothercitiesinChina.
2.Beijingisbigger/largerthananycityinSingapore.
Beijingisbigger/largerthanallthecitiesinSingapore.
注:北京的确属于中国,不属于新加波范围内.
不过不知道楼主是不是自己生造的句子:貌似新加坡只有一个城市.