Picking a favourite part of France is a real difficulty , the country having 3 coast lines, 2 mountain ranges and everything between is a big ask. Food varies one part to the other, so I suppose I like all of it.
One place not mentioned is the Ile d' Oleron I love it there, I don't think it is typical France a bit of an Islander mentality going on but nevertheless I can think of worse places in the world.
Ironically one of the few difficult places to wild, the one occasion I have witnessed the police moving folk on but a little municipal campsite, clean and shaded pitches, scoffing oysters, sun on your back ( St Georges near Boyardville)
Mainstream France I think I would re visit the Pyreenees .stunning ,breathtaking a vista on every turn.
A lot mention the COte D'azur lived there for 12 months in Frejus , So St Tropez, Monaco, Nice Grasse etc great places for a day out ...the hidden jewel of the area is Lac du cassian .....A bit like Woodhead but with Sun .!!
As you can see a difficult question