In this matter, the female character does not necessarily have to be older than the man -- although I admit to enjoying the idea of Marion Zimmer Bradley's grey-haired characters, Sex in the City's Samantha Jones, and even Joss Whedon's Inara (who was arguably older than some of her clients) for that very reason -- but rather, that she is the one who has experience in matters of love, intimacy, or interpersonal relationships is something I find interesting especially if the girl is, well, still a girl, herself.* (In fact, you can also play off this stereotype where the cute, sparkly chick is the one who is the least innocent, and her love interest -- although rich, smart and handsome -- is completely floored. "Shiny!")
If you're old enough to remember Jeff Bridges' endearing portrayal in "Starman", you might remember how boyishly innocent he was in all things -- from swearing to (not) smoking a cigarette and screams of fright to apple pie -- and how that, more than anything, kept Jenny Hayden by his side. The same could be said for the lionesque Vincent from the cult classic, "Beauty and the Beast". (This is long before the Disney and Broadway versions, and gives us a glimpse of Linda Hamilton before she became a tough-gal for the sake of John Connor.) Catherine is more knowledgeable than Vincent in many ways and yet she is ignorant of his world -- their love long remains floating on a 'Rainer Maria Rilke' tide of innocence. [Although their chemistry reminds me most of Buffy and Angel, BTW -- cheesy as the time-gap may be.]
Pete Garey of Ariel and Joscelin of the Kushiel's Legacy are accomplished fighters and killers, only "innocent" in body. (Thus placing them firmly in a separate camp than Angel et al.) However, that is the most poignant thing effecting their relationships with Shaughnessy and Phèdre, respectively, and the stories acknowledge how these women's sexual knowledge encroaches and affects the lives of these men...something both gents rail against right from the start. Wesley (aka The Dread Pirate Roberts) is excluded from this esteemed company only because his beloved is, arguably, more innocent than he in every way.
This is also not a "cougar" relationship -- the goal is not to prey upon the male, or insinuate that she is only interested in the conquest of younger men, but merely that there is a set of circumstances wherein the female MC is the one with the knowledge/power (in this singular sense), where she holds the reins of choice and she may choose to share that knowledge or not, knowing what crossing that line may bring. He does not. (Or, like Pete, maybe he does and decides that it's not worth it! Losing Ariel vs. losing one's virginity is something even a fearsome magician like Malachi can respect.) The young man looks to our heroine with curiosity, even hesitation, in the wake of this larger-than-life, unknown thing and she is the one who must proceed slowly, carefully, reverently or withhold her desires with iron will. There is an awesome tension in this.
There is no tension when the male character rushes up screaming "Corrupt me! Corrupt me! For heaven's sake, PLEASE!" like a pimply boy from a John Hughes movie or pushed into the spotlight like some 40-year old virgin; it's Peter Pan mistaking thimbles for kisses, or Lily and Jack's chaste trysts in enchanted woods, or the wide-eyed innocence before corruption when William was merely William the Poet as opposed to "William the Bloody" or the irreverent "Spike". The allure of innocence is in its magical moments, the ones that are cherished for their fragility. It's approaching the other person with the shy, tentative smile while bringing a candle that's "extra flamey" or being the sole object of attention, grokking the other person entirely.
Is there a place for this sort of role-reversal in modern YA storytelling? Or is the Prince Charming myth too close to our hearts? Is the older/experienced man who holds the slipper, the kiss, the key to a girl's innermost fulfillment too deeply entrenched for the idea of a girl's tentative exploration of a more virginal lover to work? Is it too foreign a concept to draw readers in? Does it demand too much from a passive romantic ideal?
I'm curious. But, then again, my husband is two years younger than me.
* This does not necessarily mean sex, either (in any of its many colorful definitions). Being "experienced/knowledgeable" is not something solely belonging to ex-virgins, but more a familiarity or comfort with bodies, touching, physicality, personal space, romantic relationships, the game of attraction, etc. You most likely know what I mean.