Every year the Tate invites nominations for the Turner Prize from members of the public. And every year that's the last we hear of them. Someone assured me that the fate of these public submissions was to be solemnly poured into a waste-paper bin in the presence of the laughing judges. Perhaps that story is not true, but it might as well be.

This year it was different. When the four short-listed artists were announced in the summer, it was stressed that while two of them – the film-maker Isaac Julien and the imaginary space-maker Mike Nelson – were the judges' choices, the other two – the photographer/videoist Richard Billingham, and the waggish conceptualist Martin Creed – were the choices of the public.

Which is to say, the second pair had been chosen from among those suggested by the public, by the judges. But since they were artists who an art-world panel might well have chosen off their own bat, I'm not sure what the difference is. Still, whoever loves them, work by these four can now be seen in the Turner Prize show at Tate Britain.

Richard Billingham is best known for his photos showing scenes of everyday life in his family home, featuring his fat and tatooed mum, his small skinny dad, slobbing around, fighting, swinging the cat and drinking and smoking themselves to death. One or two are good pictures – his mum doing a jigsaw, for instance – though they stay solidly within their genre of picturesque ghastliness. None of these are in the Tate. Rather there are some recent landscape photos, of absolutely no interest, and two video pieces, one dwelling on his dad lying half stupefied in bed of a morning, and the other of a young man smoking, but smoking backwards, the film being reversed. The production values are slack – bad picture quality, meandering hand-held framing, variable focus – in ways that don't contribute much.

I saw a film by Isaac Julien about seven years ago and since then I have been careful not to see another one. How right I was. Wow, can this guy not make films! The Tate has two pieces, a two- and a three-screen projection. Fantasias of (mainly) gay male desire is Julien's schtick, in sequences that proceed with frictionless dreaminess. He has no sense of building a rhythm. He has no sense of composition, other than symmetry. He has the corniest ideas of the beautiful and the sensual. He's stuck in the stock-cupboard of gay imagination – cowboys in cowboy hats, ballsy Latin women. He cannot direct actors to save his life. He likes dance. And although it doesn't usually matter to me who wins the Turner Prize, I must say that if Isaac Julien wins – and I believe he is the bookie's favourite – the world will feel a stranger place.

Mike Nelson's work typically takes you on a story through a sequence of fabricated rooms and corridors, spaces that are always poor, messy and dilapidated, and which feel almost real, as if you had actually wandered into some deserted minicab office or motel lobby. They usually contain some odd note – a weird object or furnishing – to imply strange, absent lives. Or that's what people say. But it's never really worked for me – partly because I think: why go to an art venue to see a pretend cruddy place when I have plenty of real cruddy places in my life?; partly because the strangenesses (eg "sinister" masks) seems too formulaic; but mainly because, though Nelson has a keen eye for authentic detail, the almost-reality effect never actually happens.

In this show it nearly did. The trademark crud-chic is still irksome, but the installation, a run-down office corridor leading to a large storeroom full of shelves holding a not quite rational assembly of junk, is unusually well fabricated. If you're lucky enough to be in there by yourself, you can just believe you've trespassed into some institutional backroom area – and this sensation of half-believing while knowing it to be a fiction is quite exciting, like a conscious dream. But when other viewers come in and start chatting and poking around, the illusion fades at once. And without it, the contents and layout of this imaginary place aren't quite imaginatively rich enough.

Martin Creed's forte is embodying the inconsequential, encapsulating the transient, making felt the tiny but telling difference. He constructs things that involve small but precise changes. He incites reperceptions or reconceptions of the existing facts.

His works include a piece of paper scrumpled into a perfect sphere, a caption that alerts the visitor to the fact that a doorway is very slightly obstructed by a table, and a room half filled with inflated balloons entitled "Half the air in a given space".

A sense of precision is crucial, the sharp definition of phenomena that are barely there. And though this may sound like a bit of a waste of time – well, "a bit of a waste of time" sounds in turn like a work by Martin Creed. In short, in this marriage of Zen and nerdiness, Creed has created a definite sensibility.

His piece here is impressive in its je-m'en-foutisme. There's a large room, quite empty. At regular, frequent intervals the lights go on and off, on and off. That is all. So what is on public display here are the very conditions of gallery display, and what's more a gallery event, morning and evening, never normally seen by the public.

Yet I'm not quite sure that it works, at least for the sort of first-time viewer the Turner Prize show is aimed at. With any piece by Creed, you really need to know some others to pick up the tone, and this would hardly be the best to start with. And besides, using the Tate's standard lighting system, as the conception requires, results in rather vague lighting changes, that half fade and half flicker. So the event in question is not very sharply defined. But it's OK.

The prizewinner will be announced on 9 December by Madonna. Turner Prize 2001 is at Tate Britain to 20 Jan, 020-7887 8008