Considering my rather cynical view of anything having to do with romance in real life (my full written opinion of Valentine's Day, for example, is ten pages long and full of expletives), many people are surprised to learn that I am perhaps the ultimate romantic when it comes to fandoms in general and fanfics in particular. Yes, I was an XF MSR; in Star Wars, I was one of the very first Mara-Luke supporters (YES! VINDICATION! BWAHAHAHAH!! TAKE THAT, HAMBLY!); and the list goes on. There is no quicker way for a fanfic to get my attention than to mention that it deals with a relationship between two characters. Even unlikely pairings entice me--I'll hold my breath until I see if the story is worth half a $#!+, but I'll read it.
Unfortunately, the poor romances drastically outnumber the good ones. The poor ones have a lot in common; and so, in "honor" of Valentine's Day...well, you get the picture.
Boy, does this one ever cover a lot of territory. SNERT is a term that, I believe, orginated with a friend of mine to describe AOL pests; it is an acronym for a Snot Nosed Egotistical Rude Teenager. The word I like to use to describe these kinds of people is "gushing," and it's a trait that runs over into romantic fanfic. These are the kinds of stories where nothing ever goes wrong, everyone's happy-happy-HAPPY, where the author can't seem to get enough of talking about how wonderful it all is. These are the kinds of fanfics that cause people to die of saccharine overdoses. Just about every bad romance fanfic ever written that hasn't completely massacred the characters or isn't even legible falls into this category.
While I'm not as hostile to the genre as I once was, I should still note that Sailor Moon is by far the worst offender of all in this category.
Mary Sue and her male counterpart, Gary Stu or Marty Sam were born, as with the rest of the modern fanfic age, of Star Trek. To put it kindly, they were self-insertion fanfics whose purpose was to pair the author's depiction with Kirk/Spock/etc. And they were treated with all the respect/applause they deserved (that is to say, not much).
Closely related are "Mary Jane" fanfics, where the chosen character isn't supposed to be the author him-/herself, but the purpose is still the same in a romance fanfic--to pair said character off with the desired canon character.
Bad enough. Worse still are when they have jealous cousins--the authors--who are determined to do the utmost damage to any rivals for their character's beloved's hand--in reputation, if not physically.
Two examples from professional fanfic, the Star Wars series of novels--Barbara Hambly's Children of the Jedi and A.C. Crispin's Han Solo trilogy--stand out in particular. COTJ introduced the character of Callista, Hambly's Mary Jane for Luke Skywalker. (She wasn't suited for this, or any other part, of the role Hambly cast her for, but that's another story.) At the time, there was only one real "rival" for Luke's affections--Mara Jade, who was introduced in Timothy Zahn's Thrawn trilogy and, at the time of COTJ, had a working friendship with Skywalker which many (myself included) believed should develop into something more. In the series immediately prior to COTJ, Kevin J. Anderson's Jedi Academy trilogy, Lando Calrissian had made a widely telegraphed and very transparent pass at Mara. Hambly wanted to get Mara out of the way--so she inserted a scene that did everything but announce to the world that not only had Mara fallen for that pass, but that she and Lando were regularly sleeping together. (Because of this, I, along with many others, saw a kind of poetic justice in the character assassination Callista suffered at the hands of Anderson in Darksaber.)
The Han Solo trilogy was even worse. Crispin was forced by canonical concerns to remove her "special someone," Bria (who I think is a full-fledged Mary Sue) at the end of the trilogy; apparently taking the stance "If I can't have him, no one can," she struck out not just at rival Leia, but at Solo himself--asserting that at the beginning of the Star Wars movies when Han first met Her Royal Highness, he was on the rebound from Bria. Fans of both Leia and Han were justifiably outraged.
For another textbook example, from a different fandom, of how not to deal with potential rivals, I recommend (and believe me, I use the term extremely loosely) the treatment of characters Sabin and Shadow in a Final Fantasy VI fanfic called Setzer's Christmas.
I could just as easily put this one under SNERT syndrome--hell, this is the frickin' cause of SNERT syndrome--but because the first rule of every story is that there must be complications, I'm going to give it its own slot.
To put it simply, even in a romance, you need drama, which means you need complications. REAL complications. Problems that are serious. Even the canon of Sailor Moon has a number of real and serious complications--especially early on--with regards to the relationship between Sailor Moon and Tuxedo Mask. Fights, rivalries, and disappointments were all there, and they were all real. They weren't solved in five minutes, and often not even five episodes.
Go ahead, lay them on heavy! Don't give your characters problems with easy solutions, then try to build suspense by having them act like complete idiots for ten paragraphs/pages/chapters. The harder things are for your characters, the better. And here's a novel suggestion--don't have a happy ending. Happy endings are a dime a dozen. Make the romance a tragedy. Have the hero propose to the heroine with his dying breath (ref. Cloud Cover, a Final Fantasy VII story). Or worse.
It's a tall order, but let's face it--romance is the hardest kind of story to do well under any circumstances, but it's the one that, when done well, will hit your reader the hardest. And a well-done tragic romance is the height of the genre--after all, which would you rather have, Romeo and Juliet or Twelfth Night?
And an addendum to this one:
Generally, if your story has this problem but not the previous one, it means you've fallen victim to the "limp fist" cliche--that is, you throw up one last obstacle out of the blue (or resurrect one previously laid to rest), creating one last bit of suspense for your heroes to (easily) overcome on their way to absolute bliss. NO, NO NO! I can GUARANTEE you that this will be a petty problem; the only suspense will be whether the reader turns away in disgust. The last obstacle that your heroes overcome should be one of the first ones introduced; it should be present throughout the story; it should be unresolved; and it should be significant!
The pure romance story exists almost nowhere today, and for good reason. If your story is anything longer than a vignette, then you'll need some sort of outer frame for your story that doesn't revolve around your main characters' relationship. In the best love stories, that framework actually becomes an integral part of the romance without it seeming that way; the two worlds stay separate for the most part, but as the story goes on, the one begins to intrude more and more in the other, and vice versa.
And, finally,
Don't take it for granted that your readers already know and love the characters you're working with; in fanfic especially, where everyone and their uncle has a different take on the great ones, it's important to remember that while you can take past events for granted, you can't take personality for granted; if you do, your readers will either judge your characters to be acting out of character or--worse--simply not care.
Meanwhile, I'm still out there, reading through the Internet slush pile in search of gems. Maybe I'll get lucky and find a few more. Maybe one of them will be yours.