PBase

How about one central place that lists the images in descending order of hits across all galleries. Today we can only see this for a period of a few days..

If you mean your stats then see your profile - http://stats.pbase.com/

In addition to the statistics Dave pointed out, you can try PBStats. This is a program that user Srijith wrote, when you run the program it generates a report with the hits for all photos in descending order.

http://pbasewiki.srijith.net/tools