On Sun, 25 Feb 1996, Jon K. Hayashi wrote:

What qualities make a good fanfic?  What qualities make a bad fanfic?  Is 
there
any sort of quantifiable that beginning writers can use or is it simply "I 
liked that one."?  How much of it is mechanics vs. type of story vs. genre?

mechanics = continuity, writing style, etc.
type of story = crossover, continuation, lemon, etc.
genre = Ranma, AMG, BGC, etc.

I believe the most important thing for any writing is to write about 
something that interests YOU.  I write for myself and only seldom go 
back and rewrite so that it can be read by others.  

If you want to make available what you have written to others, then and 
only then do mechanics, et al, come into play.  The mechanics are 
simply that, and anyone can get help on cleaning them up (although a lot 
of people should at least use a spellchecker first.) ;)  If you also want 
your story to be popular, then you may want to consider type of story and 
genre.  I will take the trouble to read to completion any well written story 
regardless of type or genre.  

Please be aware that the fanfic list is here to help with mechanics and 
to allow your stories to be previewed by others.  I don't consider it the 
proper place for finished stories (although I am happy to see them.)  
This results in stories of widely varying quality.