Gentlemen, think about this for a minute.
Why is it that WWII makes such good game play. When WWI, Korea, Vietnam, and modern combat doesn't?
Its all about balance.
WWI the Axis planes ruled the skys for 2/3rds of the war. Then the allied planes caught & exceeded them, and it was one sided the other way. Granted it flipped back & forth a few times in the middle. But trying to find any one period where planes were equal in capability is virtually impossible. It didn't happen that way.
WWII you have a constant flow of new planes from all sides. Armament is better, and its more about the pilot than the plane. In short, you are close enough to balance to make for good game play.
Now, where do you see balance in modern Planes?
Not to mention that game play is not the same when you don't even have visual on your enemy when you've locked on, fired, and killed him.
Korea, possibly, esp if it concentrated on early war. Late war WWII prop planes and a few early war jets, like the Navy F9f Panther carrier jet that did close air support. If they did do Korea you'd have to end it at the point where air to air missiles start becoming effective. Concentrate on the early war.
WWII had such a wide diversity of planes, with vastly different capability's.
This translates into balance, and fun. For almost each plane one side had, there was a a plane, or a tactic that countered it.