There was an unmistakable horror vibe at this year's BFI Flare, as the London LGBT film festival is now known. The lineup included a strand of 80s frighteners with certified gay appeal, including The Lost Boys and A Nightmare on Elm Street Part 2; an indepth talk on queer slasher history; a tongue-in-cheek feminist house-of-horrors installation called Killjoy's Kastle; and Monster Mash, a short about gay gorehounds hooking up at a Halloween party. (One comes as Carrie, the other as Regan from The Exorcist. It's cute.)

Of course there are lesbian, gay, bisexual and transgender fans of horror, a genre packed with alienated yet sympathetic figures forced to create strange, thrilling new lives outside mainstream society. But the appeal goes deeper than personal identification. Horror is the realm of the unquiet dead, a place where hands burst from graves and corpses lurch to life – grotesquely fantastical expressions of very real psychological truths. One way or another, hidden histories, repressed emotions and neglected traumas will out. Pain left to fester will erupt from the past into the present. And it won't be pretty.

That's why there's reason to be cheerful about a wider shift in LGBT film-making that has nothing to do with horror, but everything to do with acknowledging and embracing the past.

Almost any gay film festival today will include examples of three overlapping kinds of film: stories with period settings; documentaries about LGBT history and heritage; and films about older characters. Call it a backward turn – but backward in a good way. This fascination with the past is less about nostalgia than about taking stock, raising awareness and preparing for an uncertain future.

There has always been queer onscreen expression, overt or covert, but it was only in the 90s that an LGBT film movement gained widespread recognition. This was New Queer Cinema, which emerged from the Aids crisis and collectively constituted an expressionistic cri de coeur of alienation, anger and desire. (Think My Own Private Idaho, Poison, The Doom Generation.) As legal, social and medical progress was made, the dominant tone of LGBT film-making softened from radical revolt to aspirational accessibility, favouring coming-out tales and opposites-attract romcoms about accessing love and acceptance on basically mainstream terms (Beautiful Thing, Jeffrey, Latter Days).

Pride, which relates the unlikely alliance between a London lesbian and gay group and a Welsh community during the miners' strike in the 80s. Photograph: Nicola Dove

With the battle for marriage rights nearing its endgame, at least in America and Europe, that access now feels almost like a given. Apparent legal equality is an apt time to take stock, consider one's position, even let one's guard down a little. With less demand for big-screen expressions of either cathartic angst or romantic wish-fulfilment, we have instead witnessed a kind of gay cinematic present-mindedness in small-scale, naturalistic, bittersweet titles such as Weekend, Keep the Lights On and I Want Your Love; and a willingness to explore grief, so often deferred through the years of struggle, in the likes of Last Address, Tom at the Farm and Lilting, a forthcoming feature starring Ben Whishaw as a man in mourning obliged to deal with his late partner's mother.

Most noticeably, though, the past has returned. The most prominent form of the backward-looking LGBT feature is the period piece, now entrenched as mainstream producers' preferred mode for presenting gay stories. After Brokeback Mountain and Milk came A Single Man, Behind the Candelabra and HBO's recent adaptation of The Normal Heart, starring Mark Ruffalo and Julia Roberts; coming up are Roland Emmerich's film about Stonewall, and Pride, about the unlikely alliance that a London lesbian and gay activist group struck up with a Welsh valley community during the 80s miners' strike.

Commercially, period stories benefit from the safety of distance. Now that it is socially and politically extreme to suggest that LGBT folks are lost souls or perverts undeserving of legal protection, medical treatment or basic empathy, it is uncontroversial (and less financially risky) to tell stories in which they confront, and preferably overcome, such prejudice. If they are true stories, like Pride, so much the better for fostering sympathy. Representations of acute current issues facing the queer community are thinner on the ground – don't hold your breath for a studio picture about the murder of a homeless teenage trans sex worker – but let's not be mealy-mouthed. The cultural enshrinement through movie-star cinema of key moments in the fight for LGBT equality is a development worth celebrating.

If the merit of those films is linked to mainstream visibility, the main value of the recent wave of LGBT documentaries lies in community history awareness. Relatively cheap, frequently revelatory and often benefiting from extraordinary archive material, this work sets down stories that might otherwise be lost. Notwithstanding the occasional crossover success, such as How to Survive a Plague, about early Aids activism, these films are largely seen by LGBT audiences at festivals and at home, and concerned with niche subjects. Some are about locations – the terrific Wildness, Continental and Age of Consent depict a Los Angeles bar, a New York bathhouse and a London fetish club respectively – but more often they are about artists, activists or other individuals of note. Recent subjects include erotic film-maker Peter de Rome, Australian nightlife entrepreneur Dawn O'Donnell and trans teacher and writer Kate Bornstein. Out this month, I Am Divine tells the story of the taboo-busting drag performer and muse of John Waters, Divine.

The vital thing about these titles is that, even though they look back, they aren't going over old ground: their subjects tend to be unfamiliar even to LGBT audiences. As much of the community's attention has shifted to mainstream assimilation and narcissistic consumerism, traditional channels for the transmission of the unique heritage of queer experience – not least intergenerational gossip – have withered. Documentaries can redress this deficit, helping non-straight audiences locate their own experiences without having to reinvent the wheel or forget painfully learned lessons – and, of course, allowing them to encounter fabulous individuals from the past. I Am Divine, for instance, broaches still-live issues such as body image and family rejection.

Cheng Pei-Pei and Ben Whishaw in Lilting. Photograph: Artificial Eye/Sportsphoto/Allstar

Gay men, the gag runs, cease to exist when they hit 35. Yet LGBT cinema today is increasingly interested in people who lived through past eras. Sébastien Lifshitz's documentary Les Invisibles, about a range of older French gay and lesbian people, was a trailblazer in this respect, even giving rise to a spin-off photography book. The American documentary Before You Know It covers comparable ground. In fiction, the ever-iconoclastic Bruce LaBruce's latest feature, Gerontophilia, is a lovers-on-the-lam story about a beautiful young man and his septuagenarian boyfriend. Meanwhile, UK film-maker Nathan Evans is pursuing funding for The Grey Liberation Front, a romantic comedy about a mismatched couple who meet as care-home residents, to star Simon Callow.

Such films are the most intriguing facet of this backward-looking turn. They are Janus-faced: older characters are conduits to the past, embodiments of different times, carriers of knowledge that remains invaluable; yet they are also a glimpse of the future, living now where the young must go. With HIV a manageable condition (for those in Europe and America) and fewer LGBT people content to fade into middle-aged invisibility, the idea of a queer future seems less and less like the contradiction in terms it once seemed. Films about older people, who – spoiler alert! – turn out to be just as sharp, fun, sexy and fallible as kids, are ways to explore this terrain.

There is a lot more to a queer future than personal experiences of ageing. The advent of same-sex marriage brings us to unknown territory. Legal protections, however just and welcome, won't magically undo centuries of culturally ingrained abjection. People who aren't straight will still sometimes feel like outsiders – but they will be participating in mainstream institutions, too. Will alternative experiences familiar to many LGBT relationships, such as non-monogamous relationships and multiple parenting, enhance marriage for all sexualities? Will there be a homophobic backlash? Will the queer movement radicalise against assimilation? Movies such as Concussion, about the dissatisfactions of a bourgeois lesbian marriage, are already starting to ask these questions. But we won't know the answers for at least a generation.

A generation ago, the legal triumph of women's lib prompted comparable questions, which were explored through science fiction in marvellously exotic and absurd extrapolations by writers such as Margaret Atwood and Ursula K Le Guin. Before this current backward-looking turn, the horror genre helped LGBT audiences feel the past. After it, perhaps SF will help us feel our way into the brave new worlds ahead.

• I Am Divine is out on 18 July, Lilting is out on 8 August, and Pride is out on 12 September.

• Remembering Peter De Rome, gay porn pioneer