Though the IL2 series is showing its age, it is still the best WWII flight sim out right now. With its ability to interact with scourched earth you can fly whole squadrons against enemy air and ground targets rather realisticly (for a russian made flight sim) If you do not mind the P-51 acting anything but a P-51 and the Mossi being a slow hunk of wood..its a good game.

LoMAC is the best of the modern sims but is very complicated and turns a lot of people off.

Waiting for the new BoB from the makers of IL2