As a fanfic author myself I find this thread quite entertaining. ^_^
I'll admit there's a lot of crappy fanfiction out there. I will never understand why people who are so obsessed with a show/movie/comic/anime/whatever that they have to write their own stories about it can't be bothered to take the time to make sure their stories make sense and are readable. When I write I will not publish my work online until it meets both criteria... with one notable exception where I was intentionally trying NOT to make sense. Don't ask. That story's a piece of crap and needs to be deleted before anyone else sees it.
Um, getting back to my point, while there is a lot of crappy fanfiction out there I find once someone starts posting a lot of good quality fanfiction in a fandom the people posting crap get intimidated by the comparison and stop posting. This may or may not be universal, but it has been the case in my experience. Those who can't be bothered to write well don't like having the crappiness of their work highlighted by proximity to higher quality writing and tend to look for somewhere else to publish their crap.
In case you were wondering, I publish fanfiction based on the Saturday morning cartoon show the Winx Club. Yeah yeah, I know, it's a kiddie show and the art is a little simplistic, but there are some seriously hot babes in that show, if you ignore the fact that they all look anorexic. On top of that the social dynamics of that show have a lot of untapped potential that I love to explore. If anybody is interested you can find my work at adultfanfiction.net
in the Winx Club area of the Cartoons section. You will have to enter your date of birth before you can read the stories. AFF has had to protect itself against potential lawsuits from parents of underage kids who don't take "Go away until you're 18" seriously.
Forgot to add, if you want a fandom that was just made for crossovers try Sliders. Every week they landed in another weird alternate version of Earth with its own strange rules. Thanks to Quinn Mallery's interdimensional wormhole they could wind up in ANY fandom! I once toyed with the notion of having them slide into the SGC only to have Quinn's wormhole get tangled up around the Stargate, rendering both wormholes unusable. It would take the combined genius of Quinn Mallery and Samantha Carter to get the two separated while in the meantime some sort of crisis loomed that could only be averted if the Stargate was useable.
Simple Simon met a pieman going to the fair;
Said Simple Simon to the pieman "Let me taste your ware."
Said the pieman to Simple Simon "Show me first your penny."
Said Simple Simon to the pieman "Sir, I have not any!"
Half-elves and golems and nymphs, oh my!