How many other games than Aces High have survived (let's for argument's sake, say that AH1 and AH2 are the same game) as long? We're nearing 15 years now if I'm not mistaken.
Not only in flight sim genre (is there even more than 100 players on Il2 anymore?), but all games types considered. As far back as Ultima -- really an unlimited, all-time, all-type, all-platform comparo.