Even before the prolonged gush of the awards season, there's been a lot of adulation in the air of late, with much of it directed at a pair of Britain's most battle-hardened film-makers. Mike Leigh has justly had his reputation burnished by Another Year; and even before the release of 127 Hours, the bouquets have been prepared for Danny Boyle. But perhaps we could spare a thought for another, currently less exalted grandee – Terry Gilliam, who recently celebrated his 70th birthday without much in the way of a surprise party from an industry that seems to be showing every sign of having forgotten about his very existence.

It's a strange situation for those of us for whom Gilliam has been a square-peg fixture in film culture as long as they remember watching films at all (one of my own formative experiences came with Time Bandits as a doubtless snot-nosed nine-year-old). Brazil will always be the pinnacle, but in everything he made between Jabberwocky in 1977 and 98's Fear and Loathing in Las Vegas there was at least one moment of genuine brilliance. Now though, he looks becalmed, his cinematic future seemingly given over to endless stuttering attempts to finally make The Man Who Killed Don Quixote – an exercise in windmill-tilting whose first act was already covered in 2002's glumly compelling documentary Lost in La Mancha.

But now, as the saga moves into its second decade, Gilliam's whole recent career starts to feel less like documentary, and more like fiction. It could almost be the basis for one of his own movies, based on Cervantes but spliced with Sunset Boulevard and Withnail and I – the outlandish, tragic story of a veteran maker of marvellous creations consumed by doomed obsessions in a rambling pile in north London while going ignored by an indifferent, dimwit world. You could call it King Terry.

In the absence of concrete progress with Quixote, his attention for now is likely to be focused on an imminent sidestep into opera – a production of Faust due to open at the ENO next spring, the physical potential of the link-up such that you're only surprised it hasn't happened before. But I can't help feeling it may be some time before we see that trademark baroque swagger on screen again. Certainly, our tight-fisted new age doesn't look promising ground for a film-maker whose finest moments came with his most soaring flights of imagination, and whose flights of imagination often came with a hefty price tag. On the set of Twelve Monkeys (still one of the best art films Hollywood ever made), he's known to have doggedly stuck to the task of bringing the film in at its $30m budget – but in times like these, where would another $30m come from?

It's a problem thrown into sharp relief by the recent arrival of the penultimate Harry Potter movie, a project untroubled by financial constraints, and one that by a rather cruel twist of fate was released just a couple of days before Gilliam's big 7-0. Because alongside the starring role for Don Quixote, you sense that if King Terry were ever to be made that Potter with his all-consuming, zillion-dollar success could surely take the part of cackling villain. After all, not only have the films settled on a visual style much given to blatantly Gilliam-esque flourishes – our hero had quite the history here, JK Rowling's initial preference for him as series director ending in his rumoured blackballing by Warner Bros.

All of which means that, rather than Leigh or Boyle, the figure from British film who hoves most ominously into view when you think about Gilliam now is in fact the ghost of Michael Powell – lauded in recent weeks with the reissue of Peeping Tom, but of course, a director who while alive saw out his career frustrated and forgotten. It's a grim prospect, the idea of such a talent becoming for new generations of film lovers the one thing worse than blacklisted – unknown. Would a film-maker as humane as Gilliam really settle on such a bleak ending for King Terry? You can only hope he dreams up a better one ...