It's very easy to over state what Boyd did. As in, what he did in reality was so fantastic and unbelievable that it's very easy to attribute additional not fully truthful aspects to him.
Unfortunately, can't really talk about the YF-16's combat potential as a dog fighter all that much. But what I can say is that if you apply Boyd's earlier work (E-M theory and E-M charts) to the the YF-16, then its very likely that you -can- compare the various airplanes. While it's certainly true that the YF-16 could perform the buttonhook turn to significant advantage in a wide variety of situations (the buttonhook turn is used when being pursued. By initiating a ridiculous tight turn, you could dump enough velocity to cause the opponent to overshoot, and then MOST importantly, the YF-16 had the thrust-weight ratio required to rapidly regain the energy it had just lost and allow it to reengage), it's quite likely that either the MiG-29 or Su-27 could have beat it in other regimes. For example, look at how the F-4 (a terrible dog fighter) was able to find advantageous engagements against generally aerodynamically superior MiGs during Vietnam (aided by Boyd's E-M work).
It should also be pointed out that amongst the things that the Air Force forced onto the F-16 was a much better radar. Nearly all the major changes made to the production aircraft degraded its talents as a dogfighter (as you point out) while vastly increasing its flexibility and its ability to engage at long-range - decisions which in retrospect were massively beneficial. The biggest thing to ding the USAF with is that they did not sufficiently increase wing area to compensate for the mass increase. In other words, Boyd's vision of where air combat was heading wasn't really spot on.
Also, credit should go to where it belongs. Boyd did not design the YF-16 by himself. The rest of the "Fighter Mafia" deserve just as much credit, as well as the designers at General Dynamics.