Winx Club, the French dub. I've seen both English versions, and the French version pwns them both. All the French voices are the ones I consider to be the characters' true voices. It probably helps that French and Italian are very similar languages.
The Québec French version is regarded as this by many French-Canadian fans due to the excellent localization of the script (and, like the Spain dub, it also received Matt Groening's praise). Of course, it might be a bit unusual to hear Hubert Gagnon's Homer sound like Norio WakamotoIN FRENCH!
Well, it also has a great dub in France, and most French people find the Quebec one weird, and vice versa. Examples: The French and Québec trailers for the Movie. note the comments in both videos saying that this version is weird and the other one's better.
The French dub of Samurai Champloo is considered one of the best French anime dubs ever (especially when you consider some other dubs), with a spot-on cast, decent acting and even a few extras — it has Mugen giving Jin the nickname "Lennon", for instance.
The French dub of Back to the Future. It appropriately Woolseyized all the colorful slang, all the cursing, and had a brilliant cast of voice actors, especially Marty and Biff. (The best not-in-the-original moment would be Biff's Brief Accent Imitation when pronouncing McFly in the first diner scene).
The French dub of Who Framed Roger Rabbit; it was done by the same people who did the French version of Back to the Future, the voice actors of Marty McFly, Doc Brown and Biff Tannen are respectively Roger Rabbit, Judge Doom and Baby Herman
The French dub version of Around the World with Willy Fog makes a few improvements to the series. For example: such the two main male characters from the book, Around the World in 80 Days, are given their proper names, Phileas Fogg and Passepartout. In addition, Romy (who regrettably is not renamed Aouda as with the book) is given a voice fitting a charming lady like herself.
The French dub of Howl's Moving Castle easily surpasses both the Japanese and English versions. Something about the authenticity of a film set in (alternate-universe) France being spoken in French helps, but the voice acting is also spot-on. Howl's screams of terror at his hair are FANTASTIC, and Sophie's voices are each beautiful in their own right.
Fun fact : the French voice actors of Buster and Babs Bunny are also the voices of Ranma male and female.
The French dub of Popples. The title characters sound almost like little kids!
The French dub of My Little Pony: Friendship Is Magic has improved drastically in season 2. The Gallic references in the original are handled skillfully and not clumsily — when Apple Bloom starts speaking French in "The Cutie Pox," instead she starts speaking an antiquated dialect of French (more associated with the fleur-de-lys cutie mark) and Applejack says, "My sister's speaking weirdly!", while in "MMMystery on the Friendship Express" Gustave LeGrand becomes an Italian, Gustavo Il Grande. The voice work, which had always beena strong suit of the dub, continues its consistent quality, with Mélanie Dermont (Rainbow Dash) and Elisabeth Guinand (Fluttershy) equaling if not surpassing Ashleigh Ball and Andrea Libman. Perhaps the pinnacle of the French dubbing of Season 2 is "A Friend in Deed" (although it is given the Spoiler Title of "Pinkie Pie's New Friend"), which has a perfectly crotchety voice for Cranky (here called Grincheux L'Âne Têtu, or Grouchy the Stubborn Donkey), translates the puns well ("four evers = forever" is translated as "sept jamais = c'est jamais!", meaning "seven nevers — it's never!") and best of all, the French version of the Smile Song, "Te voir sourire", is fantastic.
The French dub of Samurai Pizza Cats have an effective voice acting, the adaptation is also pretty good and uses sometimes local references.
Wayne's World, the adaptation was made by Alain Chabat and Dominique Farrugia from the comedy group Les Nuls. The voice acting is also great, especially the smooth performance of Emmanuel Curtil (who is the usual French voice of Mike Myers and Jim Carrey).
The Broken Sword series; the French version was made by professional voice actors, of course. The most memorable performance is Emmanuel Curtil (French voice of Jim Carrey) as George Stobbart; he did a great job with the american accent of the character, without being too caricatural.
The French dub of Scrubs is really good, even the voice of Alexis Tomassian fits more for John Michael "J.D." Dorian; his nasal, piercing and half-witted voice really fits for a loser like him.
The French version of The Persuaders! and The Dukes of Hazzard, they both improved the script by adding some extra dialogues (sometimes in improvisation), the most obvious case is an episode of The Dukes of Hazzard which was fully rewrited into an episode about rillettes.
Almost any cartoon in which Roger Carel has got a part. What's really impressive is how he can take numerous (and always funny) voices. His very different portrayals of Sir Hiss from Robin Hood and Kaa in The Jungle Book, for instance, considerably diminished the feeling that Sir Hiss was a rip-off of Kaa (while in the original, it's very clear as both have the same voice). Carel is also known for having dubbed: Baisl of Baker Street (from The Great Mouse Detective), Bernard (from The Rescuers), numerous side characters in The Sylvester and Tweety Mysteries, Mickey Mouse himself (!!!) in some shorts, Kermit the Frog from The Muppet Show (a role in which he was constantly adding jokes improvised during the dubbing sessions), the list goes on. A last one deserves expanding: he did almost EVERY character in The Many Adventures of Winnie the Pooh, starting with Winnie himself. He also did Rabbit and Piglet. The most amazing part is that he dubbed the three characters in a row in scenes where they are interacting. Even to this day, although retired, Carel can still successfully do this trick, as seen in this video which is an extract from a recent interview.
The French Dub of Timothy Goes to School. While the original English version of the show is fun and relaxing to lesson to. The French voices for some of the characters like Timothy and Lilly are very cute. Special mention goes to Yoko who sounds downright adorable when ever she speaks in the French version.