Aces High
I'll endorse steepclimbs enthusiasm for Aces High. I started playing it a year ago and still play in the (free) head to head arenas. It took me a while to get used to the game, and even longer to master just one aircraft type.
I now have great recreational fun in furious dogfights (free-for-alls or 'FFAs'). It's almost a shame to shoot down Spitfires in my Zero, but theres nothing like a good deflection shot, whatever the type. Having said all that, you're always learning, and it's great to team up with different types to figure out best tactics.
A bit off the thread question I know, but there you go. Steepclimb, I fly as Dr Lecter in the h2h rooms if you ever stray out of the Main Arena.