Known as BD in France (bande dessinées, translation = 'drawn strip') comic books are very popular in France (and much of Europe), in a way that they have never been in the UK. They are generally considered to be an artform of their own, rather than light entertainment for children.
Some of the more famous characters such as Tintin have reached international fame, often because of television cartoons based on the original characters.
There is a lot of overlap between French cartoon production and (equally enthusiastic) Belgian production:
The Adventures of Tintin by Hergé - "The Adventures of Tintin" (Les Aventures de Tintin) is a series of comic strips created by Georges Remi under the pseudonym Hergé. they made their first appearance in 1929, in a children's supplement to a Belgian newspaper. The stories relate the adventures of Tintin and his dog Snowy and other characters
Asterix by René Goscinny and Albert Uderzo - "Asterix" is a tough little character, set in the times of the Gallo-Romans, where he lives in a small Brittany village not yet occupied by the Romans, but frequently attacked. There is an enormous amount of subtlety and wordplay in Asterix, making it hard for non-French readers to follow all the subtleties. the good stories remain, however, even without this.
Lucky Luke by Morris and Goscinny - Much less widely known outside French speaking countries than Asterix and Tintin, Lucky Luke is 'the fastest cowboy in the wild-west', crime fighter and generally good guy. Very entertaining.
The Smurfs by Peyo - known in French as Schtroumpfs (an invented word), the smurfs were originally invented as cartoon characters, and are now famous worldwide, not as a result of the BD, but because of the subsequent television cartoon series aired from 1980-1990 and often repeated since. Small, blue, kindly creatures who live in the forest!
Blake and Mortimer by Edgar Pierre Jacobs - based around Mortimer, a classic English gentleman, and Blake, a serious army officer who saves the day, together they have adventures of a more 'grown-up' nature than the others comic strips listed above. They have also been turned into a televised cartoon programme.