Multiplayer coop combat flight

I am looking for a flight sim like IL-2, but with better graphics. My son Gabe (10 yrs) and I are exploring flight and enjoying it. Il-2 FB and PF is quite fun but we are looking for anything prettier as far as land graphics. I have a 4 node LAN with very powerful computers that will run most anything so I'm not concerned about horsepower for the graphics. I know that FS2004 has some add-ons and MS Combat Flight Simulator had Firepower and others. I would appreciate some information on what's out there and available and for what flight sim.Chuck