I Agree that there is just as much noise, if not more, in watching games. That's why I am of the opinion that there is no way to accurately judge how good or bad a player is. We can only make arguments based on stats or what we've seen. For a good argument you need more than one type of stat. For instance, if Johnson did wel on Defensive rating as well as situational stats I'd be much more inclined to agree (or at least not argue with) the statement that he is a very good defender. In his case, different stats contradict each other.
I started rambling about boxscore stats (and their inclusion in wp and such) because of your statement that you think there are stats that can accurately judge how good or bad a player is. I already said why I didn't think Defensive Rating (and related stats) doesn't qualify and thought I'd mention a few reasons why other types of stats don't qualify in my opinion as well.
And that's about it.