Looking for Yves Montand's version of C'est si bon on YouTube there is only a one minute performance while I found this one by Eartha Kitt (a very interesting singer). YouTube says 1962 but I doubt it as the song was written in 1947 and poularized by Eartha in a 1954 movie but recorded in 1953 (Wikipedia), the same year as Yves Montand did (french wikipedia). And of course Louis Armstrong's version.
I did not know René Joly but I knew Chimène (very nice melody). It was apparently his only hit, according to the French wikipedia that also informs us he was Roger-Roger in Starmania.