pstine, in a subsequent post you mention that you received a nomination but did not complete your application. Nominations or lack there of is part of the explanation you are seeking. Some qualified candidates will not receive a nomination and some will receive more than one nomination. Additionally, the form of the nomination may constrain Admissions, that is Admissions may literally have to offer an appointment to some qualified candidates, while with others (probably the majority), Admissions will determine which of the nominated and qualified candidates meet their needs for an incoming class. Admissions' "needs" are not limited to the candidates SAT, ACT, or GPA and there is no simple ordinal ranking by which one could identify oneself as being "best".
Suggested initial reading may be found in the Nominations sub forum stickies starting here:
Congressional Nomination Guide
And finally a tome which all applicants should read:
Why didn't little Johnny or Janie get an appointment?
There is also a Rand Study regarding USAFA admissions which provides some additional back ground. Threads in which it is mentioned may be found here
. Ultimately, Admissions has a difficult job in that they are trying to identify the "Whole Person" attributes which will allow one to succeed at the Academy and subsequently as an officer in the Air Force.
The good news is that over 1,000 applicants to each SA succeed in this process each year. Although, to succeed you must complete the process. Good luck.