If you've read the "Boyd" biography mentioned here by other commenters, you'll recognize many of Boyd's and Sprey's criticisms of the so-called "F-X" fighter procurement program (which eventually led to the F-15) in his critique of the F-35. [1]
None of the Fighter Mafia actually "designed" any of these aircraft, but Boyd, Sprey, Christie and others did play a pivotal role in changing how the Pentagon defined and proved the specifications of the fighters it was buying. The F-X was supposed to be a larger, swing-wing, multi-role behemoth, similar to the abysmal F-111, which Boyd proved to Pentagon brass to be inferior to virtually all enemy fighters, by way of his brilliant "Energy-Maneuverability" theory. In this way, Boyd and Sprey influenced the final design of the F-15, but to a much lesser extent than the designs of the F-16 or A-10. [2]
One key point Sprey brings up in several of his other interviews on the F-35 topic (which he curiously leaves out of this one) is that, regardless of the capabilities (or lack thereof) of the F-22 or F-35, neither will ever be as successful as the historically-great fighters like the P-51, F-4, F-15, or F-16, simply because they'll never be built in sufficient numbers.
For a fighter to be great, its pilots must also be great, and to do that they must train regularly and often, something which has proven impossible with the low dispatch reliability of these complex fifth-gen fighters. Sprey notes that in WWII, the U.S. P-51 fleet triumphed over the vastly superior German fleet of ME-262s, by first developing tactics that could defeat this amazing jet (i.e., shooting them down while taking off or landing), and because there were simply more P-51s available to fight.
Sprey and Boyd were right about a few things: build them light (which helps make them fast and maneuverable), build them cheap, and build lots of them.
[1] http://en.wikipedia.org/wiki/McDonnell_Douglas_F-15_Eagle#Or...
[2] http://en.wikipedia.org/wiki/Energy%E2%80%93maneuverability_...