I think there is a big difference between the amount made and rarity.

There is no question that from the amount made,

Year 2000 $25.00 Cinco de Mayo
Sammy Hagar $25.00
Cure $25.00
Van Morrison $100

IMHO a tie for 5th between several chips

As far as difficult to find, as pointed out, the first issue numbered roulettes might be rarer than any of the limited editions.

To add more controversy there were only single examples of some prototypes so take your pick.