Hey Khoa, I think that "Plus belle la vie" is one of the most popular, although I strongly dislike it. However, there are a lot of interesting series such as "caméra café" or "kaamelot" that are quite good but they don't make use of formal frenc per se. So my question to you is: What is your level in French? If your level is beginner, I would advise you to look into cartoons dubbed in French in order to tackle the basics of that language. On another note, I am French and I do not like French TV series because I find that they lack originality. You will make your own choice but in case you find yourself disliking those series you might look into English series that are dubbed in French.