I think it depends on the airline. I flew through Paris a couple of weeks ago and there was some decent duty-free shopping. The wine and champagne selection was quite nice. There was also a nice make-up and purfume selection with some sample packs of different dior lipsticks etc. I was flying Air France so I was only in their terminal.
How long is your layover? Mine was 7 hours so we had time to hop on the train and go into the city!
What is your final destination? Frankly, Duty Free stores are pretty much the same at every airport. CDG does have a good perfume selection, and it's fun to browse the little mini-supermarket. BUT the little mini-market is horrendously overpriced. I really don't think that the shops at CDG carried anything that you couldn't find here in the US, and the prices weren't any better, especially with the Euro/Dollar exchange. Now if you had time to actually shop in Paris, that's a whole other story...