Provence - Bonnieux, Ventoux and Dentelles is good. Tends to be rocky natural traversing singletrack with sustained descents. Although Ventoux is tough and long to ride up, the descents can be as much as a 1500m. It's 1909m high. 'Cailloux'.
Embrun area Southern Alps. Some good stuff. Plenty of well marked, ie no map reading, trail centres with easy topos.
Pyrenees. Only been to Ax-3-Domaines area in the Ariege valley. Very good singletrack. Very quiet. Some cable car routes.
Esterel. this area is inland and on the coast near St Raphael/Grasse. VTOPO do a good guide for this area. It's in french but you can relate the route descriptions to the IGN 1;25k map easily. I did one amazing route last summer 800m ascent and descent, the BRAMAFAN swithcbacks. It had 2 miles of 4inch wide sheep trail that snaked slightly dhill, enough to roll.
I'm a teacher so do 5-6wks MTBing, Climbing etc every summer in the ALps, Pyrenees or Dolomites.
Morzine was disappointing and had too many ski access tracks.