For French language fantasy, if you're open to graphic novels, definitely try to find a copy of Légendes de Contrées Oubliées, by Bruno Chevalier and Thierry Ségur, a short 3-book series from the late 80s — early 90s, gorgeously drawn in colored inks, which, without spoiling the intrigue, starts as what seems like a classic epic fantasy story but eventually turn into a very original (and cynical) take on the ideas of quest, divine rule and foundational myths (although do mind it's also a fairly dark and violent story). It has a cult status in France and has been reprinted several times, but to my knowledge it has never been translated into English.
See also my recommendation on page 52 of this same thread for The Quest for the Time Bird (la Quête de l'oiseau du temps), another French dark fantasy graphic novel with similar theme and from the same time period (late 80s), though this one has been translated into English, and currently the French edition appears to be out of print (though I expect it will get a new printing at some point, that series is also pretty well liked).
Outside of graphic novels, I haven't read Alain Damasio's la Horde du contrevent (it's been sitting on my shelves unread for years, ahem), but I have several times heard it recommended as one of the best French fantasy books, with lots of innovative ideas and novel takes on the genre.