Well, I come from a CS master's of the university of Nantes and I don't feel _at all_ like I have a lower level than if I went to one of those schools. It's clearly the other way around.
I would hope so since Epitech/Epita is bac+3 whereas a CS master is bac+5. Although I doubt many universities would still reach those schools level even after a master.
CS master of Nantes is a really high level diploma comparing to some other universities , I will get mine from the same university this year (hopefully)