Here is my end of the year list on your end-of-the-year list question.
10. They are written by people who want to get jobs writing David Letterman's lists.
9. What about end-of-the-year lists on the internet?
8. Movies and books and all the rest are organized by the seasons, so to produce middle-of-the-year lists or beginning of the year lists make little sense.
7. Years ago, David Wallace wrote a bestselling book of lists -- could it sell in the era of the internet? Why not, especially since it lends itself to internet pickup?
6. Actually, the internet, with its low-attention span length requirements, seems ready-made for lists.
5. Does anyone put out an end-of-year list about magazines, and if not, why not? (Actually, the man who calls himself "Mr. Magazine at Ole Miss. (Samir Husni)‚ used to publish an annual list of magazine start-ups and busts.) If he doesn't do it any more, there may be your answer.
4. It seems to me the internet has expanded best-seller lists in the book bus. (The Times Book Review publishes an extended bestseller list online, doesn't it?)
3. Does a list of one (like Time's "Man of the Year" qualify as a list?)
2. The multi-candidate early presidential primaries and the polling accompanying them, seem to have added innumerable listings both in print and on-line.
1. To answer your question(s), then, no they don't seem to be declining; yes, they are there to sell magazines (not to mention the subjects of the lists themselves); no, they are not becoming less relevant, because they were never really relevant.
I hope this helps.
PS Please take me off your list. (Just kidding.)