ArtReview is based in London, but its view is global. The editors mention some of the things that might affect the ranking: blockbuster exhibitions, new commissions, the value of the dollar, taste of Russian buyers, locations of auction activity, or symbiosis of curator and donor.
The editors make the comment, “...if artists have always lived in the shadow of their patrons, it’s the artwork that ultimately endures.” I’d like to make the observation that the artwork endures as long as someone cares enough to take care of it. Sometimes even bronze statues are stolen and melted down for the value of the metal. Private collections might be housed in private museums, but museums, whether public or private, depend on funding, which can shift with the political, economic or cultural winds.
I suppose it’s only human to want to rank things & people. But the whole point of what we broadly refer to as art is its meaning. And meaning is always personal and individual. It only exists if we become aware of it, discover or create it for ourselves.