Do you like jets? Do you like arcadey combat because fuck reality? Do you like dramatic war stories filled with motherfucking heroes? This is the series for you
PS1 trilogy:
Ace Combat 1/Air Combat is okay
AC2 is good but it's fucking amazing on 3DS (Assault Horizon Legacy is a remake of 2)
AC3's international version is kind of crap. Project Aces's director has actually apologized for this, citing that localization was a difficult thing for them at the time
AC3's Japanese version is fucking great and there's a translation patch
PS2 trilogy: I don't have the /v/ recommendation chart image so I'll just quote it here "Lest you be blessed to find a better game than these"
AC4 lacks route select in favor of a damn good linear story. You will cry a little
AC5's story goes into black ops territory and has you fighting to uncover a shadow war while your superiors completely forget how a plane's black box works
AC0 goes into the past conflict detailed in 5. Belkans want their clay
others:
AC6 on X360. Haven't played it due to not having a 360
ACX on PSP is pretty good but not amazing
AC Assault Horizon series:
ACX2 Joint Assault on PSP is not terrible but it was the first to take place in the real world, opening the door to the series's greatest shame:
AC Assault Horizon "Hey Project Aces, make the next one like Call of Duty" "No" "Come on" "Okay, but you'll regret it"
If you don't like the newbie-friendly jet controls that autolevel you, etc, you you can almost always set realistic control in the menu