Good 'Simulations' are:
IL-2
http://www.pacific-fighters.com/en/screenshots.php
Falcon 4
http://www.f4hq.com/default.php?page=default
Flight Simulator X
http://www.microsoft.com/games/flightsimulatorx/
Combat Flight Simulator 3
http://www.microsoft.com/games/combatfs3/
There are a pletheroa of other 'arcade' like flight games. One I have, but havent' had time to play is Pacific Storm, it combines, RTS, strategy, and a flight sim all in one...
http://www.pacificstorm.net/gallery/
If I could find a up to date WW1 flight sim similar to Red Baron or Red Baron 2, I would buy and play it...