I dont think you can really measure the quality of ones RP.
What exactly is the quality?
for me it would be a story, request, transmission etc that entertains me. Something i enjoy reading, makes me smile...pretty much like a good movie.
But there are for example some RP stories where people wrote a whole bunch of pages...spent hours creating it. And when i read it, i will most likely close it again after 2 sentences because to me it is like some news report...but not about the world i actually live in but from some place that doesnt exist...so why should i care? But it would be unfair to say the story has no quality, it simply has no value for me. Other stories might have been written in a few minutes and make me burst out laughing, cause it had a brilliant idea in it or a funny picture etc.
So the short funny story has more quality for me than the long and serious one.
But i think it depends on the reader.
so all in all i would say a RP story has good quality when there is someone who likes it.