I think that, in all forms of art, France has been consistently excellent.  However the greatest achievements of Germany, Italy or Ireland surpass French art - Goethe, the Renaissance, Joyce, etc.  Maybe this is because in France there always seem to be schools, or collectives, of artists, eg. symbolism in poetry or nouvelle vague in cinema.  The greatest artists of other countries seem to be more isolated and able to rise above and out of the group - Picasso out of cubism, etc.  Perhaps this is the same in filmmaking.