No one buys 3rd party games on the Wii... Don't see how that translates to third party developers being self-destructive.
Well these third party games all did over a million according to wikipedia as of March 2011.
http://en.wikipedia.org/wiki/List_of_best-selling_Wii_video_games
Just Dance 2 (5 million)[8]
Just Dance (4.3 million)[10]
Michael Jackson: The Experience (2 million)[8]
Guitar Hero III: Legends of Rock (2 million)[13]*
Deca Sports (2 million shipped)[14]
Game Party (2 million shipped)[15]
Monster Hunter Tri (1.9 million)[16]
Resident Evil 4: Wii Edition (1.9 million)[16]
EA Sports Active (1.8 million)[19]
Carnival Games (1.5 million)[20]
Guitar Hero World Tour (1.334 million)[21]*
Epic Mickey (1.3 million)[22]
Rayman Raving Rabbids (1.2 million)[25]
Resident Evil: The Umbrella Chronicles (1.2 million)[16]
Sonic and the Secret Rings (1.2 million)[25]
We Ski (1.2 million)[26]
Big Beach Sports (1.2 million shipped)[27]
Active Life: Outdoor Challenge (1.03 million)[28]
Call of Duty: World at War (over 1 million)[29]
Red Steel (1 million)[25]
Rock Band (1 million)[30]
Game Party 2 (1 million shipped)[15