According to the Paris Airports' website, there are no direct flights from Cleveland Hopkins into either Charles de Gaulle or Orly airport. So your flight time will depend upon where you change planes and how good a connection you get.
Delta offers flights via Atlanta (into Charles de Gaulle), with total journey times starting from around 11 hours, depending on the layover time:
http://www.delta.com
Continental offer similar journey times, but via Newark Liberty:
http://www.continental.com
easyJet operate the cheapest flights between Paris and Nice. They fly from both Orly (with a journey time of 1 hour 25 minutes and Charles de Gaulle (with a journey time of 1 hour 35 minutes):
http://www.easyjet.com/
Chris