Natalie Haynes: Did we pick the best book for the Orange Prize? That's not the point

All the books that made the Orange shortlist are really good reads - great story, beautiful prose, a brilliant theme

How do you judge one work of art against another? It's a question that bubbles up around every book, film, TV show or art prize: we're never comparing like with like, so how is it possible to claim that one book is better than another when they are novels or programmes, written to be enjoyed, not built to compete?

And voting processes are fraught with difficulty: if it's a jury prize, as at the Cannes Film Festival and most book prizes, you rely on a small number of industry experts to make a fair decision, even if they have worked with some of the eligible actors, directors or authors. The whole process runs the risk of appearing like an industry back-slapping festival instead. So wouldn't it be better to do away with prizes altogether, and just let artworks find their audience?

Well, that would certainly work if we simply want to maintain the status quo: authors who are already successful would continue to thrive, because readers would buy their new books, having enjoyed their previous work. But how do new writers then make an impact? As the book review pages of newspapers are pressed for space, and seem to get shorter almost every month, readers can rely on a prize to give them one thing: not a book they will definitely like (there's no such thing), but a book that lots of other thoughtful readers have liked very much.

The ban-all-prizes brigade says that literary prizes are worthless because they try to do something intrinsically impossible: pick the best book from a bunch of disparate genres and authors. But they are missing the point: all the books which made this year's Orange shortlist, of which I was a judge, are really good reads. They may not all be to everyone's taste, but they all had something going for them – a great story, beautiful prose, a brilliant theme – which made them stand out from the roughly six million words I have read so far this year.

It may sound trite to say that the winning doesn't matter when it comes with prestige and a large cheque – two things writers like as much as the rest of us. But making the longlist, and then the shortlist, gives a huge boost to writers' sales – perhaps as many as 150,000 more books are sold by a shortlisted writer than one who escapes the judges' attention.

And, as a rule, the more people who have read and liked a book before we read it, the better the chances of us liking it. A recent survey revealed that more than half of self-published authors earn less than $500 a year. Obviously, if you are writing merely because you love to write, the royalty cheque isn't the most important thing. But if you want to become a full-time writer, earning enough to pay the rent is an important factor.

Writers may moan about editors, but the figures of self-published writers are hard to ignore: those who pay someone to edit, copy-edit and proof-read their work earn considerably more than their DIY peers. In other words, readers, not unreasonably, prefer to read books which have been read by someone other than the author, who might gently point out that a character has changed name, or hair colour, or miraculously returned from the dead.

Last night, Madeline Miller won the last ever Orange Prize (it will have a new name and new sponsors next year) for The Song of Achilles. It's a beautiful novel, re-imagining the Trojan war through the eyes of Patroclus, the man whose death is so devastating to Achilles in The Iliad that he gives up his 17-book sulk and rejoins the war to avenge his friend. Miller's novel charts the relationship between the two men, from their first boyhood meeting to the 10-year war on the plains outside Troy.

Whether her novel is objectively better than the other five excellent novels on the shortlist is not a question which I or anyone else can answer. But it was, unarguably, the most popular book with the majority of judges of this year's prize. Other books on the shortlist ran it close, because they were differently great pieces of writing. And five different judges might easily have picked a different winner.

Having been nominated for – and then immediately lost – a Perrier Best Newcomer Award in my days as a comedian, I have never really understood why this is a problem. Just being nominated changed my career for the better. No one ever pretends that one comedian is definitively funniest; we simply accept that any judging panel, like any audience, will like some jokes better than others. And not winning was fine – the nomination was enough to boost my confidence and raise my profile.

Now the Orange Prize is over, I will buy copies of all the shortlisted books for my friends. I have already given several copies of some of the long-listed books to people, because that's what happens if you stand still for long enough near me. And when readers are finding new books and new authors, we all win.