First off, I can't take credit for either a formula or the rankings themselves, which are the work of Dan Spazierer, using the formula:
1 point per 20 yards passing
4 points per passing td
1 point per 10 yards rushing/receiving
6 points per rushing/receiving td
3 points per field goal
(The reason for this scoring in these preliminary rankings is that these are the points used in a cheat sheet contest Dan has been invited to.)
As to the rankings themselves, I was also a bit surprised by some (you may know by now that I'm a lot higher on Darrell Jackson, for instance), but I'll be the first to admit that Dan has been right an astonishing number of times when I've thought him wrong...
At any rate, we'll see what happens. Keep in mind that these are very, very early rankings, and their main purpose is to spark discussions such as this one.