IGDA put this out last week, just got around to reading it:
http://www.igda.org/casual/quarterly/2_1/index.php?id=9
"The following lists are based solely on the Top-10 lists made public by each individual game portal. A simple scoring system was used to summarize the data. Each week spent at the #1 spot on the list is worth 10 points, #2 is worth 9 points and so on down to the #10 spot on the list being worth 1 point.
Summary of Real Arcade Top 10 List November 24 2005 – September 20 2006:"