Gotta agree with everyone else. You don't have time to clear Customs and Immigration, take the RER into Paris (about 45 minutes each way), see something, take the RER back to CDG, get back through Customs and Immigration, and board. There's also not that much right around CDG (though I think EuroDisney is close). Perhaps your best bet for killing some of the time is a massage at "Be Relax" in Terminal 2.