In some of the universities you find professors with M.Sc but they cant supervise the PhD students, while in other universities this is not allowed they must attain PhD.
It is not necessary to have Ph.D. to become good professors. In India Sir C.V.Raman who was awarded Nobel proze in Physics was not having Ph.D. I know several good professors with only M.Sc. On the otherhand, I also know some "professors" who are neither good in subject nor in ehics are having Ph.D. degree. Unforunately, Ph.D. now considered as necessary condition to become professor. PERSUING in proper spirit Ph.D. does prepare our mind to develop original thinking and this may help in teacing.
I totally agree with Prof. R.V. Mehta (My Respected Senior and Dear Friend). But as he rightly said, Unfortunately, Ph.D. is considered as necessary condition to become Professor. As far a degree is considered Ph.D. is higher degree compared to M.Sc.