Infinite Jest is clearly influenced heavily by film. Many of the sequences are highly filmic in nature. Some of the surreal elements of the novel are reminiscent of David Lynch's work. And of course, the central driving plot element around which everything revolves is a film. Much of the content of Infinite Jest deals with films and directing, specifically everything involving James Incandenza. Him directing films, people watching and interpreting those films, etc. Certainly one of the central themes of the novel is entertainment and why we watch what we do, what it says about us, etc.
With all that said, an adaptation of Infinite Jest for the screen would seem inevitable, right? Well, not really. Much of IJ is so overtly literary in nature that it just couldn't be made into a film and retain all of it's structure, power, meaning, etc. However, I do think you could make a film of the central narrative threads of IJ. It just couldn't really be what IJ the novel is. But it could be something very cool, unique, intelligent and entertaining.
Some of the most filmic elements of IJ (mild spoilers):
* The opening chapter. Use of perspective so that Hal's seeming external dialogue is revealed to really be internal dialogue, and the 'switch-over' that comes at that moment. Would be tricky but could definitely be done.
* Eschaton. Like a microcosmic Lord of the Flies meets War Games. It would be awesome.
* Gately destroying the 'Nucks. This is a no-brainer. Gately could be played by Mickey Rourke. Think of a less-cartoonish version of his character from Sin City. Big, sensitive oaf, who is capable of mass destruction out of loyalty, duty or in defense of others.
* James Incandenza's visiting Gately's hospital bedside.
* Hal at the 12-step meeting near the end. It's kind of a Fight Club-esque scene (beginning of Fight Club), but more surreal and absurd than those in FC. And of course it would be hilarious.
* The mildly futuristic elements, i.e. IWD dumpsters being launched into the convexity, ATHSCME fans in background etc.
* All of the wheelchair assassins movements and activities
And many other parts, but with these sticking out particularly in my mind.
There are some things that could be omitted without losing too much. Such as long chapters about ancillary characters/events. These are necessary in the novel and don't feel like excess at all, but for length purposes chapters about Ederdy, Kate Gompert, the psychological reasons behind the failure of videophony, obsessive technical detail about everything, a shortened meeting between Marathe and Steeply etc. Much of this stuff is extremely well done and adds depth and texture to the novel, but would be simply untenable in a film.