IL-2 Sturmovik 1946 is your best buy. It encompasses all of the IL-2 series on one DVD, and there are very few WWII aircraft left out. An amazing game. It's real strength is in online play, though, so join Hyperlobby and try your luck. Your knowledge of WWII fighter tactics will suddenly become very important, at least in the more sensibly hosted games using realistic settings.
Another great, if slightly dated, game is Battle of Britain 2, a makeover of an older title originally produced by Rowan games. It enables you to fight the entire Battle of Britain on a strategic level, as well as jump into the cockpit of any given combat, and is one of the few sims that actually display the enormous formations of aircraft that filled the skies during those epic battles. It's probably your best bet for offline play.
Rowan also produced Mig Alley, a great sim that is, unfortunately, rather outdated now. I really wish someone would give it the same graphic makeover as the BOB sim, as the dogfights in Mig Alley were intense.
The designers of IL-2 are hard at work on a new Sim based on the Battle of Britain which looks to be eye-popping and will probably run great on a Cray supercomputer.
Until then, there is a (just released) incarnation of IL-2 for the Xbox360 called IL-2 Sturmovik:Birds of Prey. It is the same game streamlined (but not dumbed down..the full sim mode is still available) for console play and with nice graphics. Review is here:
http://www.gamespot.com/xbox360/sim/il2 ... es;title;4
Here's a trailer: the graphics were produced from within the game, so what you see is what you get.
http://www.gamespot.com/xbox360/sim/il2 ... deos;img;1