Sandra Bullock has much to say about true love. In Speed she drove a booby-trapped bus into a muscly embrace with hot boy beefcake Keanu Reeves. In Miss Congeniality she won hearts by revealing her inner bimbette. In While You Were Sleeping she found solace in carpenter Bill Pullman's big comfy bed. In The Lake House she navigated space-time to compulsively trade notes with … Keanu Reeves again. And in The Proposal, out now, she's the bossy lady who tricks put-upon employee Ryan Reynolds into sham coupledom to save her job.

I love Bullock's tawny tallness and I want her characters to be happy. I also want to buff her all over and comb her russet hair for hours like a keen stablehand at a pony parlour. But I rail against her fictional romantic choices and the wider treatment of love in mainstream narratives.

There are only a few approved ways to fall authentically in love. Either the proud protagonists hate each other – hello Elizabeth, Darcy, Beatrice and Benedick – before losing their self-delusions, bringing each other down a peg or two and realising their compatibility. Or a crisis throws two different types into necessary but unrealistic collaboration. Or two shy, unassuming types share a thousand daily routines enlivened by short walks to the end of the garden and back (try reading Remains of the Day for the ultimate celibate affair).

But there is another love, infinitely more vivid and piercing. That is love at first sight, and traditional narratives still don't know how to deal with it. It is easy to scoff, now that we live in a disillusioned age replete with syphilis and sexts. Easy to that say that love at first sight is really an immediate lust which will burn itself out once the pair have sported on a bed for long enough. Should it be celebrated, as it is, triumphantly, in the early scenes of Romeo and Juliet, then melodrama, pain and tragedy must surely follow. The message is always that Eros's arrows are subtly poisoned.

But what if, one ordinary day, a door opens, two people lay eyes upon each other and know instinctively (and correctly) that something extraordinary, significant and mythic has begun, whose energy flows into all the corners of their lives? This must have happened at some point in world history – but why does it leave writers so stumped and why does it rarely have a happy ending?

Perhaps the blinding light is too anarchic for an artist's desire to explain, to trace, to delineate. Love at first sight arrives ready-created, cutting through prior relationships and resetting the entire board. It's the uncanny electric real deal that makes everything else look petty, whose crackling energy is noticeable to any observer. But it's hard to put into words, so instead we get Character A and Character B plodding towards mutual co-operation.

At the cost of airing other people's soiled bedlinen in public, let me sketch a portrait of two prominent folk I know. One is doe-like and glinting. The other is tall, ivory, still and sculpted, with rain grey eyes. Neither is single. Yet everyone, friends, colleagues, know they have fallen in something at first sight. Whenever they're together it's as though an epic legend is being played out scene by scene, completely unmistakably – the stuff of myth and awe. To any external judge, their actions are morally wrong, their blistering chemistry destructive of their marriages and public reputations. Their crackling mutual absorption can't be turned to any useful purpose in society, so it's written off as cheap friskiness, sordid whim or delusion. It's the thing that people yearn for all their lives and almost never experience. Everything they say about it is true – but it won't be coming to a cinema near you any time soon.