IL-2 1946.
when I was just a kid, there were two WWII flight sims that captivated me, Aces of the Pacific and Aces over Europe. after that, I stopped gaming for a number of years and didn't get my hands on a flight sim until 2003 when I bought the original IL-2. the flight modeling really impressed me and I've yet to play another flight sim that has satisfied my desire for flight as much as this has.
admittedly though, the only other 1C product I've tried is the Theatre of War demo, and while I did enjoy it, it runs quite poorly on my computer.
