Ace combat 6 turned to use the same twist as ace combat 4, having the story being witnessed from someone outside the war. the young boy in the Usean side and the woman trying to find her familly getting back to gracemeria.) adding a real human value to the story.
Ace combat 5 rely on a very twisted plot and everything is there in front of you since the beginning (the legend of the razgriz) , Ace combat zero was different shorter (but harder) and having the storie being reconstructed by a journalist year afer (also witness testimony was changing depending of your gameplay) but it was a good complement to learn how the Ace combat 5 war was possible.
Also as a fan from the beginning, i found fun to play ace combat 4 in the usea in the opposite direction that Ace combat 2 did.