sorry to bring back an obviously dead topic, but I wish to add my two cents into this, grammar, chat speak all of that is one thing that leads to a bad Fanfiction, but really the worst time is...
It's almost IMPOSSIBLE to be original these days.
This doesn't just apply to Fanfiction, but AMVs, and fanart, almost everything has been done, anything new is basically similar to an older item, I mean how many fanarts have to seen of the Naruto cast cosplaying? AMVs, sure they may be different animes with the same song, but the style they were made are rather similar (such as my Listen To My Voice being similar to My Last MOVE and my Until The Day I Die similar to another's AMV under the same name)
Fanfics are the same, if we set the whole grammar, horrible formatting and all that stuff aside and just focus on the plot, tell me... how many of them are truly unique? I've really only been hanging around the Naruto section, and aside from the mass of yaoi, there are many High School fics, Obito survives (and isn't Tobi) fics, rewrites of the original plot (guilty...totally guilty to that one) and Harry Potter crossovers.
Hell even when you think your story is unique, you'll probably find yourself using an element that's overused, I'll break down my recent story to show what I mean, even then... I may still be wrong (Ryuusei no Kyuubi)
Rewrite of the original Naruto plot - Overused...totally overused.
Shippuuden Ages in Part One - Haven't found another fic like that - Assuming Original
Crossover with Ryuusei no Rockman - First - a fellow writer asked for permission, allowed, dropped after first chapter.
X-Over with Rockman (In general) with Naruto as the dominate anime - Second - Terra Ace was the first, asked for his permission, granted
Calling Sasuke Duck-Head and/or Duckie - heck, we do it all the time, totally not original, but totally funny.
From the summary and title alone, a story may look 100% original, but when broken down, we know it isn't... my new story is probably only around 50% original, and if you ask me, that's quite a feat.