There's no great hostel in France because there's no hostel culture
Most of the hostels (auberges de jeunesse) are public.
In Paris the most interesting hostel is St Christopher’s.
Great building but horrible location.
The rest of the parisian hostels are low quality.
To open hostel in France especially in Paris will cost you lot of money.
French laws about building, fire safety, disabled access; urbanism and architecture are very complicated.