tinyE: I have to split the category in order to squeeze in one of fave shooters of all time (and a horrifically underrated game to boot).
Fave Flight Sim is IL-2 because of craft variety, looks (given it's age and I can't un the really new fancy looking stuff) and the ability to adjust EVERY little detail to make it as realistic or unrealistic as you like.
Now, my fave "Flight/Fight Sim" is Heroes of the Pacific and it is a true gem for anyone who doesn't want to be bothered by things like "gravity" or "physics". Cool WWII settings too with all sorts of groovy torpedo runs, dog fights, and even a POW rescue.
Needless to say I am biased toward anything thing in the air during WW I or II.
Hmm, GOG should get Heroes of the Pacific. That sounds like good fun.
My all time favorite which is arcade oriented but just great is the Lucas Arts classic:
Battle of Britain: Their Finest Hour
God, I loved that game back in the day in glorious EGA! It looked fabulous and it was so damned fun. I loved manning the bomb sight and dropping bombs although I was not especially good at it. And the dog fights were awesome. I really hope GOG can get that and Secret Weapons of the Luftwaffe at some point along with much more Lucas Arts goodness of course.