As I said in my original post it's really the entire Fighter Rank recipe that determines 'effectiveness'. The K/T and K/S debate Shane and Dip are having brings up a case in point.
K/S: Largely determined by the ammoload and gun type of the plane you are flying. For example a great pilot may have a 2.5 K/S in a 205 but 5.0 K/S in a Niki. It doesn't mean he's less effective in a 205, or less 'good' it just has alot less ammo and not as many cannons. Also gunnery skill greatly increases K/S as you are getting more out of your ammoload. Plane choice has alot to do with K/S
K/T: This is more complex. From a plane perspective a plane that climbs great, is fast, and fights best low, La7 for example, will have a great K/T comparatively. From the pilot perspective base defense and fighting from and to CV's greatly enhance K/T. On the other hand hunting bombers seriously hurts your K/T. Plane choice and engagement type selection have alot to do with K/T.
There are so many factors that go into each sub-stat it's impossible to say which, if any, determines 'effectiveness'. Some say Hit %, some say K/T and some say K/S. I say fighter rank is actually a pretty good 'overall' indicator of 'effectiveness' as the sub-stats themselves are so interdependant and in several cases mutually exclusive. Also, plane and/or engagement choice can distort one or more sub-stats significantly making comparing one person's stats to another's dangerously presumptuous as Levi mentioned. Therefore, the only real way to measure 'effectiveness', if that is even possible, is to combine them as as Fighter Rank does.
Anytime someone asks me how to get good rank, I sum it up like this. Perform some rather dull and annoying chores for bomber, attack and vehicle and kick alot of arse in a fighter. There is no real way, other than perhaps exclusively vulching to obtain a sub-100 fighter rank other than kicking alot of ass. To a small extent you can substitute some bellybutton kicking by just flying alot, but that only gets you so far. In the end Fighter Rank is either ALOT of vulching or alot of bellybutton kicking or some healthy combination of the two. Some methods of kicking bellybutton may be good for your K/S some methods for your Hit %, K/D or K/T. But, if you have a good fighter rank (sub-100), which factors in all of these things combined, you indeed kicked some bellybutton (and/or vulched alot).
Zazen