I don't think there's a better WWII era flight sim currently available (at least until this company releases their upcoming Battle of Britain game). The engine has been updated with enhancements for more-modern systems, and it still looks pretty good. I still play it frequently, and still don't feel like I've experienced half of what this game has to offer.
This simulator is about two things:
#1 - Staggering variety
#2 - Staggering realism
You can tone down the latter if you want to just kick the tires and light the fires. You can easily build "quick missions" with some drop-menus to explore battle possibilities --- like how the American P-80 jets would have fared against the German ME-262 jets (both jet aircraft were in the war, but I don't recall that the P-80 was ever saw combat).
There are dynamic campaigns, static campaigns, instant missions, tons of fan content out on the web, and literally hundreds of flyable aircraft - and hundreds more non-fliable - from nearly every era and nationality (although a lot of the different aircraft are different models of certain aircraft - and believe me, this flight sim is realistic and detailed enough that it really does make a difference). The Russian front is perhaps a little more detailed than most, but this game includes the Pacific War expansion which allows you to fly in carrier and island battles across the Pacific Ocean.
Online, multiplayer gaming rocks with this game, too.
I don't think I can gush enough about this one. So I'll just stop now.