I always liked Birds of prey, though wished it had a null/dial-modem linkup. Perhaps something like that with TCP multiplayer support? Air Warrior comes to mind, too..
Ooh yeah, I LOVED Birds of Prey. Had an analogue joystick to use it and once you turned off the "easy" mode that was on by default it was a fantastic game to play, and sometimes quite unforgiving. Coupled with being able to fly something like 30 or 40 planes (albeit with the same cockpit graphics) and even a chapter in the manual about the physics of flight, I reckon it was one of the most detailed from a flying point of view and for me at least, about the right level of realism.
The terrain was a little bit lacking however...
