THIS is the greatest painting in Britain?

The National Gallery in London recently took a poll on "The Greatest Painting in Britain," and here's the winner: The Fighting Temeraire by
J. M. W. Turner.

Frankly, I don't get it. I mean, sure, it's an important, symbolic work fraught with melancholy meaning for the British. Painted in 1838, it depicts an old tall-masted gunship being towed up the Thames for demolition. And although Britain at the time was still the world's dominant superpower, that dominance had been shaken by the Revolutionary War and the War of 1812. Perhaps Turner was looking ahead, and the sun on the right is finally setting on the British Empire, not just on the scene at hand. But does all that significance mean that this rather dingy composition is a greater painting than, say, Van Gogh's Sunflowers or Caravaggio's Supper at Emmaus, both of which were also nominated?

Count me as one who doesn't think so. But then, I'm not British.