if you have to pick up your luggage and check in again..... no
for only changing gates and passport, security control ...yes

You'll have to check with Delta to see if they can issue you two boarding passes, otherwise you'll have to check in with Air France once you clear passport control. If this is the case, then two hours will not be enough.

As I suggested on your other thread, take the train direct from CDG to Nice - cheap, relaxing, and you'll probably get there at the same time or sooner.

I think they may check your luggage through. But the flight from Paris to Nice is domestic - so you will have to go through Immigration in Paris (and possibly also recheck luggage).

I would never risk it. If several planes land at once it can take you 30 to 45 minutes to taxi around, find a jetway, get to Immigration and wait on the long line for non-EU passengers. Then possibly deal with luggage, getting a new boarding pass, a new security check line etc.

A couple of years ago I booked a ticket to Paris and a separate ticket on Lufthansa to Frankfurt. The Lufthansa agent would not book me a flight that left 2 hours after arrival at CDG; she insisted on a 4 hour window.

Assuming your points are on Delta, telephone the SkyMiles desk or e-mail your questions. You will have a slightly better chance of reaching someone in the know.

Even though your flight is non-stop that doesn't guarantee that it won't be late. I've rarely arrived at CDG on time from the U.S.

It can also be a pain to get through immigration at CDG. Sometimes, they're really fast, sometimes not so much. Last time I went into CDG our flight was late and the passport control agents were on break...we waited for 30 minutes in line while they finished.

I like St. Cirq's idea of taking a train to Nice. I adore train travel and particularly love train travel in France.