I assume you are flying CDG-FRA-EWR or CDG-MUC-EWR, all on LH.

At CDG, you will have your choice of the Lufthansa business or Senator lounges. The food is slightly better in the Senator lounge, but they are otherwise much of a muchness. The Star Alliance lounge and the RCC are in the non-Schengen part of T1 at CDG and are not worth clearing passport control twice (once to leave Schengen, once to re-enter).

If you are connecting through FRA, you can go to any of the Lufthansa F lounges. Your flight from CDG will probably come in to Concourse A, so the easiest F lounge to reach will be upstairs in A (though it is located before passport control, so leave a few minutes to clear it upon leaving the lounge; there is a dedicated line for F passengers). If you have enough time, you can also leave the terminal, cross the street, and walk to the First Class Terminal. The amenities are more or less the same as in the lounges, but I understand it feels a bit more exclusive, and you will be driven to your plane. (I have never been myself.)

If you are connecting through MUC, there are Lufthansa First Class lounges there.

The first class lounges have very elaborate food and drink and are much better than the Senator or Business lounges. Stay away from the Tower Lounge at FRA (the business lounge in the area where flights to the US leave from); it is a zoo.