I've been to all the French regions, so far, except for Alsace-Lorraine and Burgundy. My favourite has been Dordogne / Gascony. It has so much variety: prehistoric caves, natural beauty (rivers, gorges, forests), castles / chateaux, outdoor experiences (canoing, hiking), beautiful villages, gastronomy (not just goose liver), wine (Bordeaux, Bergerac) ...
With two weeks, you could add a second region. I loved Provence, but then it was not so much about sightseeing as just relaxing and becoming a temporary local in our chosen town (L'Isle sur le Sorgue). Rent a villa with a pool, day trip to Nimes / Pont du Gard, Avignon, St-Remy, the Luberon, Cotes du Rhone wineries ...
Also enjoyed Normandy (military history, seafood), Savoie (mountains, cable cars, hiking, fondue), Loire (cycling, chateaux), and Languedoc (Carcassone, cassoulet, beaches) ...