Clearly, there's truth to that statement when you are looking at the "long run". BUT I could sit and watch a B&M game of poker for as little as one hour and quite easily tell you which players are 'good' and which ones are 'bad'. But that wouldn't be by watching their stacks shrink and/or grow.
Very true, I was thinking of players with nearly equal skill, but your right.

However, looking at a player's understanding and mastery (or lack thereof) of some of the tactics and skills I listed above, does; at least to some extent.
I see.

But even if we figured out a way to compair someones play to a "perfect" player, I dont think we could even agree on what a perfect player is.

Hmm, Very good food for thought.

Along the same lines, I wonder how much of the diffrence between a good player and a great player is just the ability to play grear poker 99.9% of the time instead of 80% of the time.