In the 80s, his tunes were very poppy (listen to "Tombé pour la France" for example) but, as time passed and his tastes evolved, his songs became much more refined and probably less commercial.
He has worked with pretty much all the greats of French music (some were also his idols, in particular, Françoise Hardy and Serge Gainsbourg) making tunes for them or performing duets. He studied English at the university of Rennes, has always enjoyed going to London or New-York to work with English speaking producers or musicians and doesn't mind singing in English once in a while.
Etienne Daho - Tombé pour la France
Etienne Daho - Week-end à Rome
Etienne Daho - Bleu Comme Toi
Etienne Daho - Comme un igloo
Etienne Daho - Idéal