There are no single "best" cellist, but if you mean recognition,
Emmanuelle Bertrand won the 2011 "Diapason d'or (Gold Diapason) -
Artist of the Year" price, a competition organized by the national
radio France Musique and the magazine Diapason.
There is also a list of French cellists on French wikipedia but
this site does not allow me to mention their URLs, you need to
search for it.