Hello Satanus,
I am perplexed. Frankly there are so many that I have enjoyed that it is hard to begin to give a recommendation. I will say that any of these films noted at this link, all of which I have seen, may not have made millions of $'s but are all creative masterpieces. http://frenchfilms.topcities.com/Great_Films.html.
I would even place the Swiss film industry above the US in creative style. One of may favorite Swiss films which is near France is entitled ( as close as I can remember ) 'Thirteen Days In The Life Of Jenny'. I saw it once in the 70's and have never been able to find it again. It is an absolute masterpiece and follows the last thirteen days of the life of a young girl tortured by her adolescence. If you can track it down, watch it. I guarantee that it will change your life. I am not sure how much money it grossed, but it is a good film nonetheless.
As for French comic films. *Any* film by Jaques Tati is a must in the comedy genre. I doubt whether one comic film-maker anywhere has not been influenced by Tati's style. My particular favorite is 'Jour De Fete'. An unforgettable film. Most peoples experience of French films begins and ends with 'The French Connection'.
Take care Satanus - HS