if I had to choose IL 2 1946 and CFS3
I say go for IL2 1946
the flight model is tricky but not hard to get the feeling of it.
once you have the flight model under control, the feeling wont be lost
the game isnt a system hog its quiet friendly for your system and has very nice graphics, the cockpits are very detailed and there are a lot of planes to fly.
the campaigns are alright, some are dull some are very immersive in the way of attacking ground units , intercept a flying formation of transport planes. or you have to take off very quikly as enemy aircrafts are in the area attacking your base.
in case you want some different kind of game you can play Multiplayer.
the multiplayer is really good as most server run missions that contain dogfights, attacking a naval convoy or ground targets.
join up with other players in a flying squadron of bombers and escort them.
the server I play on are very mature, and friendly.
the only reason I have CFS3 installed is for Over Flanders field mod (a WW1 supermod)
preview: