I just really like this city,shanghai.这里shanghai是city的同位语
I just realy like shanghai.如果对方知道shanghai是个城市的话,这样说就行
I just really like shanghai as a city.我是真的很喜欢上海这样一座城市
I just really like such a city of Shanghai.我是真的很喜欢像上海这样一座城市
I just realy like the city of Shanghai.我是真的很喜欢上海这座城市.