众所周之上海是中国最大的城市

As we all know, Shanghai is the largest city in China.

As we all know，Shanghai is China's largest city.

1楼翻译的更好一点

It is known to all of us that Shanghai is the largest city in China.
(-0-不过上海不是最大的吧？？）

It is known to us that Shanghai is the largest city in China.

众所周之上海是中国最大的城市
As we all know that Shanghai is the biggest city in China.
或者
It is known to all that Shanghai is the largest city in China.