Well, with our understanding of the Light Side of the Force we can understand the negative effects war has on a Jedi, we also have knowledge of how many forms said Jedi mastered, as well as the feats they accomplished. Standards like lightsaber form mastery, the Force, and say, the ability of a bounty hunter, remain the same - and it is this that we can use as a 'measuring stick'.
A Problem I see, is the fact of what is truly the measuring stick for a Jedi/Sith dueling prowess? I mean seriously what is it? In Episode 2 Anakin was easily bested by Dooku, but in Episode 3 turned around and beat him like Dooku was a Novice. Sure we have many people who stand out with a light saber, but look at Jaina Solo. Yes many hate the EU, but I think in a pure lightsaber duel, she could go toe to toe with Mace and stand a chance of winning.
Again without a real good measuring stick and seeing battles where we actually SEE different jedi stack up and actually fight[which will never happen] I fear we will never know which side of the question is actually right.
And then there's just logic. Mace Windu invented his own lightsaber form and defeated the most powerful Sith in galactic history in lightsaber combat - that in itself gives considerable weight to the lightsaber prowess of the PT Jedi Order.