I think we are looking at this from the wrong angle. Let's take Hurin and Turin as our examples.
Can we really say that one was better than the other? Say we work out that Hurin was 0.00001% better than his son. Does that mean that if they played out a one-on-one fight 100 times that Hurin would always win? Of course not.
Hurin might have been disturbed during his sleep last night and so not quite as prepared as Turin. Turin might step in the one little puddle on the ground thus losing his balance ever so slightly during a critical point of the fight.
So for two similar cases, (Hurin and Turin, Legolas and Gimli, Boromir and Faramir) I think it's inappropriate to conclude that one is a better fighter than the other.
It's like in football: Brazil and Argentina are two of the best in the world right now. But circumstances dictate; I would not say that one team is better than the other because the two have proved in recent times that they can both defeat the other. Neither is best, they are two of the best, and possibly the two best.
There are clear cut cases: Aragorn is a better fighter than Gamling, say. As for the original list, we can eliminate some. Get rid of Legolas and Gimli, obviously. Hurin and Turin would come very near the top of everyone's list, but there's no definitive order to place those two. All we can really say is that Hurin and Turin are near the top, not which one is at the top.
EDIT: For the sake of argument (i.e.
my argument) let's just suppose that Hurin and Turin were on the original list.
Ah, we've moved on to the history of Middle-earth by now, right?
Right? You all saw it, I didn't start it! If you don't want to, then my points are still applicable. Just sub Hurin and Turin with....um.....'Gorn and Boromir.