In Hong Kong, students who want to be a doctor have to apply for an undergraduate programme and they will get a MBBS degree.
For students in US, they have to apply for a graduate programme and they will get a MD degree.

As MD is a doctoral degree and MBBS is only a Bachelor degree, is it true that even if I got a MD from a non-famous medical school, my qualification would be higher than a MBBS degree holder from a famous medical school?

The MBBS is not recognized in the US. The MD is recognized but in order to become a physician in the US, you must pass both an english and medical proficiency test. Then it is most typical that you would take a residency at an accredited teaching hospital.

Hope this helps.

Keith