The research bods at EEDAR have got their abacuses out and calculated that Wii games are more prone to "price protection" than titles on rival machines.
What's price protection? Price protection occurs when a publisher of a game that isn't selling offers its game to retailers for a lower price, allowing stores to get rid of excess stock quickly. If this happens too soon (EEDAR defines "too soon" as "when a title's third month average selling price has decreased by 20% or more from its original average selling price"), it is known as "early price protection."
Anyway, EEDAR found that 15.1% of all Wii software goes through this process, compared to 7.5% on Xbox 360 and 9.09% on PS3. What does this disparity say about Wii software? EEDAR analyst Jesse Divnich thinks it backs up the theory that third-parties struggle on the Wii because they and retailers have "overly aggressive expectations" for Wii games, and that it proves "quality is one of the most impactful features for a video game."
Or, in a nutshell, Wii has waaaay too much half-assed shovelware.