This list does NOT imply that these games have sold the most units on the service. The "measure of pleasure" essentially denotes how much time players have dedicated to these games.
In fact, #9 on this list is actually #1 in terms of units sold going by the data provided by the Nintendo Channel*. My Pokemon Ranch has sold at least 109,000 copies on WiiWare (~$1,090,000 in pure revenue) as of April 8th.
[May 3rd edit: After realizing that I jotted down erroneous data for FF4: The After Years, I have updated the preceding paragraph to reflect which game has actually sold the most units according to the data on the Nintendo Channel.]
So without further delay (except for the jump), I present to you all ...
WiiWare's Top 10 "Measure of Pleasure" (as of April 8th, 2010)