Halfway through what is likely to be viewed as a non-vintage, drink-as-soon-as-possible Berlinale, I've been pondering the question of how to rate a film festival in critical terms.

After all, anyone's view is influenced by the films they happened to catch there, whether they satisfied their cravings (cutting-edge Asian, Euro auteurs, tasty genre titbits), plus some less professional factors such as the contacts they made, the flirtations they indulged in and the quality of the food and drink (if the latter were the main criteria, San Sebastian would be far and away the world's best).

The other problem is I'm always called on to make these assessments on the last day of the festival, sometimes even earlier, which means the festival and its films have not had time to mature. They have yet to play to real audiences; they haven't run the gauntlet of the awards season; and most importantly, they have yet to earn a place in one's mental cinematheque.

Passing the test of time

There are years when the consensus weathers well. The much-derided Cannes 2003 competition line-up still looks like one of the weakest in living memory - and not just because of Brown Bunny. Does anyone remember the dirge-like Tiresia' And whatever happened to that other great advertisement for French cinema, Bertrand Blier's fluffy Les Cotellettes' But time can also reveal festivals to have been a little over-hyped. Cannes 2006 was praised as a 'vintage year' at the time, but a number of its highlights (Babel, The Caiman, Marie Antoinette) faded fast, and in retrospect only Volver, Summer Palace, Red Road (I'll stick my neck out on that one) and possibly Pan's Labyrinth are heading for classic status. Cannes 2007, on the other hand, is getting better with age.

It's not just the quality of the films in competition that determines a festival's critical weight. One of the great strengths of Cannes is its sidebars: few festivals have the confidence to relegate films such as Control or Caramel to non-official sidebars (both screened in Directors' Fortnight in 2007). Then there's the festival's place as a seedbed for new talent: Berlin, Rotterdam and Sundance are all strong in this respect.

Finally, there is the key question of the number of influential world premieres. Toronto is one of the world's best festivals for seeing films, but an important part of its remit is to serve Canadian and US audiences and critics who don't visit Cannes, Locarno, Sarajevo and Venice; many of those who do will experience a sense of deja vu.

Introducing the Fest-o-meter

So here is my stab at a handy portable Fest-o-meter for marking the major players on the world circuit out of 10. Festivals score zero to five points for the quality of the competition; zero to two points for the quality of the sidebars; zero to two points for the number of exciting first-time directors revealed (in other words, I can't wait to see their next films); and one point for keeping the number of competition films that are not world premieres down to two or less. If nothing else, it has the merit of lending a veneer of scientific rigour to a heavily subjective judgment. My scores for the Big Three Eurofests from 2007 are:

- Berlin: Competition three; sidebars one; new talents one (Michael Arias, Yau Nai Hoi); premieres zero (17 out of 22 films). Total: five.

- Cannes: Competition four; sidebars two; new talents two (Eran Kolirin, Anton Corbijn, Nadine Labaki, Lucia Puenzo, Shira Geffen and Etgar Keret); premieres zero (18 films out of 21). Total: eight.

- Venice: Competition four; sidebars one; new talents zero (just one, Tony Gilroy, is not enough for a point); premieres one (21 films out of 21). Total: six.

Sure, it's clunky - but it'll do until someone comes up with a better idea...