Nrchy, I must say that I am confused by your take on this subject. You pose the question "What is the standard...?, not once, but several times; yet you won't accept an answer that is in fact eminently logical and practical. What is your answer to your own question? That there is no standard to be used? Unlikely. If so, why ask the question?
The easiest answer is in fact that "if it sounds good to you...". Why? Because music should not be overly analyzed. Music is about emotions, and (I'm thinking about another thread currently running right now) if a listener cannot be moved by good recordings of say, Mahler 5 or Billy Strayhorn's "Blood Count" on a "boom box", then there is too much preoccupation with the gear and not enough openness to the music.
However, and it's a big "however", audiophilia is a hobby, a very noble and rewarding one, but a hobby nonetheless. And an intrinsic part of this hobby is the quest for perfection in the reproduction capabilities of one's system. I think that most reasonably sober audiophiles acknowledge that this "perfection" will never be achieved, but the quest for it sure can be fun and if kept in it's proper perspective can enhance one's enjoyment of the music immensely.
I am impressed by the fact that you seem interested in the search for a standard. I'll say again. IMO live unamplified music is the best standard, if a standard we must have. I don't see why you let the questions of "what kind of instrument is being played" or "how many people are in the hall" etc. become road blocks in the acceptance of the live music standard. Clearly, these things will affect the sound of a recording. So what? There are far more aspects to the sound of music that characterize acoustic performance, that are far more important, in the scheme of things; generic traits of live sound, if you will. Complexity of timbre; something that is seriously diminished by the amplification process. Microdynamics; where a lot of an artist's expressive subtlety is manifested. And many more things; some that can be described easily, and many that defy description. The more live performances that a listener attends, the more these things become obvious; this is the key.
It really doesn't matter if you don't know the "sound" of the Village Vanguard, although, obviously, it would be ideal if you did. But if you played "Waltz For Debby" on two unfamiliar systems (or components) and one let you hear clearly that there is quite a bit of distance between the bandstand and the bar in the back, where a tremendous amount of glass tinkling and conversation is taking place, or that the slightly hooded sound of the piano and cymbals is classic "ceiling is too low" sound. While the other system masks these qualities and makes the instruments sound as if recorded in a studio, and the voices of the rude audience members sound as if they are right on stage with the musicians. Guess which system I would pick as probably being more faithful to the original event? On the other hand, if this music had in fact been recorded in a studio, with the inevitable reduction in complexity of timbre and absence of any natural ambience, combined with all of the "judicious" use of reverb and "natural" panning choices; not to mention the reduction in groove factor caused by the players having to listen to each other over headphones, as opposed to being connected by the same acoustic. What would we be able to tell using that recording? Not a whole lot IMO. Can it still sound good? Of course it can. But we are talking about establishing a benchmark for the hobby.
Anyway, I'm finding that I am repeating myself. Ive enjoyed reading and contributing to this thread. I would encourage everyone to check out Harry Pearson's (The Absolute Sound) writings and opinions on this subject. While some here will dismiss him as a pompous ass, IMO he does as good a job of dealing with this subject as anyone I have ever read.
Good Listening.