As pontifex said, Falcon 4: Allied Force came out a few months ago. However, be aware that deep down this is the same Falcon 4 that was released in the late 90s, so the graphics are a little behind, but it's much more stable than when it was first released. I have it, but haven't had the chance to play with it too much because it is very in depth. You quickly realize there's a reason why the Air Force sends cadets to a four year academy and atleast two years of advanced flight training before they even think about sitting in an F-16.
If you want to play online, I think the best option is Il-2 Forgotten Battles with the Aces Expansion Pack and the Pacific Fighters addon. Lot of people are playing these online, and some people have created some great online wars. The single player aspect of Il-2 is a weak point, but there are addon campaigns that can drastically improve things.
Right now, these are the two flight sims I'm involved with. There's also Battle of Britain II: Wings of Victory that is supposed to be pretty good if you like that scenario. Just be sure to install all the patches to get it working correctly. I would also check out
SimHQ for a good group of forums and articles relating to all things sim, especially flight sims.