Can you picture it... A flowing gown and your Prince Charming on your arm on the happiest day of your life? Okay, in order to complete this story the horses should be white. That's what fairy godmothers are for.
Okay, so maybe all stories don't get happy endings. Charlie didn't in "Flowers for Algernon" by Daniel Keyes. That is okay for most fiction, but definitely not for romances. Romances must have a happy ending or the publishers won't pick them up.
Now, you can have elements of romance without the happy ending, but generally those are not labeled romance. So, if you are writing a romance follow the formula. Boy meets girl, boy loses girl, boy and girl live happily ever after. The story centers around the romance, even hinges on it. It can have other elements like a mystery, magic, thriller, etc., but a romance must have "and they lived happily ever after."
In John Dunham's Diary, I have elements of romance, but the story doesn't fit the romance category. Perhaps, in Twilight Dance, the story might be considered a romance, because it follows the formula and ends with a happy ending.
I hope this cleared up some of your questions. Here are some links.