Back to point: what makes a fanfic good?
  And so far I've come up with the following critera:

1. The author feels it's good (the easiest part)
2. Readers tell the author and others it's good
3. More than five people read the story and think it's good
4. Pre-readers catch all the little glitches in the story
5. Long descriptive passages describing minute details of a Stephen King
novel
6. Said fic must exist for an extended period of time
7. Said fic must be recognized by established reviewers as good
8. Said author mustn't be overly desparate for C&C or MSTs
9. Said author must've written about something that makes sense

"That's my story and I'm sticking to it."--JMS, creator of Babylon 5.
"If you go to Z'ha'dum, you will die."--Kosh, Babylon 5.
"Jump. Jump now!"--Kosh, "Z'ha'dum," Babylon 5, making some sense.

Simply put, the single, first, and usually most important factor
deciding a fanfiction's fate is if the AUTHOR likes it. Ie: likes his
own work, likes the story he wants to tell, etc.

That lesson I learned long ago, and I still feel it is most important.

GT and myself have left our work for months at a time, re-posted it, and
still new people draw to the work we have done. Some people go even
longer, like Zen, or Todd Hill (sorry todd, couldn't help it), and many
others, and they come back to it, and still recieve attention.

Yes their writing is good, and great.
Yea the content is noteworthy.
The grammar, etc. . .

But NONE of this could happen, if the author didn't care about his/her
work. If they don't, then there is no foundation to put good grammar and
nice story and everything else that goes with it.

Example? I just posted Cast Not Such Dreary Countenance 1 again after
its original writing in the middle of summer of 97. I only got 3 parts
out, and accquired quite a few noteworthy remarks for my work, but other
things took my attention away from writing. Last week I picked it back
up, remembering the fond quality of the 'what-if' story I was telling,
and revised it greatly; correcting, drafting, and revising from the CSY
staff. I posted a matter of four hours ago, and already 6 people have
emailed a reply, two quite lengthy.

I know I could get that kind of reply if I didn't like my story. WHy
would they if I didn't?

Everything after that is subject to the reader's taste. :}

-TJ
-Colliding SYmphonies head
-FFIRC head
-. . . machine head