You probably know "Tintin" by Hergé (he's Belgian, not French) - an animated movie about his adventures were done not too long ago by Steven Spielberg based on two albums: "Le Secret de la Licorne" and "Le Trésor de Rackam le Rouge" - and "Astérix" by Goscinny and Uderzo (both French).
There are many more which are considered classic BD, including:
- "Lucky Luke" by Morris which is about a cowboy in the Far West that "shoots faster than his shadow",
- "Alix" by Jacques Martin which is set in the time of Julius Cesar,
- "Blake and Mortimer" by Edgar P. Jacobs (he's Belgian) which chronicles the incredible adventures of an MI5 agent and a nuclear physics professor, and
- "Les Aventures de Buck Danny" by Jean-Michel Charlier, Victor Hubinon, and Francis Bergèse which is about the adventures of a group of fighter pilots after World War II.
Today's BD has much evolved from the so called French Belgian school and the appeal has widened to more mature audiences.