Some people still really like the offline duels against all the various aircraft.  This guy has written extensively about them in his site:
The Pilot's Flying Guide to W.W. I and W.W. II Aircraft (By Chuck Hawks) 
To read this, go to chuckhawks.com, Naval and Military History, Combat Flight Simulations, then the flying guide.
After I told Chuck about Aces High, he tried AH and modified his article to at least mention AH. But his focus remains on Warbirds and all the offline duels.  
Chuck is a super detail guy with much expertise in guns, cameras, astronomy, and various other topics. Check out his site.  Well worth your time.