This thread is stirring up the pot without actually looking at any real history. Nintendo games have won GOTY many times at a variety of sites. It goes without saying that picking one game for the entire year is going to leave a lot of great ones out. To the OP: If you actually play Nintendo games you would realize that although they do have many sequels each one introduces a lot of new ideas and game play elements. They are arguably more inventive in each new 3D Mario than most new IP's that come out year to year. And there have been a lot of years they've been rewarded for it...
Edge
2014 - BAYO 2 (Wii U)
2013 - GTA V
2012 - Halo 4
2011 - SKYWARD SWORD
2010 - MARIO GALAXY 2
2009 - Boarderlands
2008 - Uncharted 2
2007 - Halo 3
2006 - Final Fantasy XII
2005 - RESIDENT EVIL 4 (GameCube, Wii)
2003 - METROID PRIME
GameFAQ's
2013 - ZELDA: A LINK BETWEEN WORLDS
2008 - BRAWL
2007 - GALAXY
2006 - TWILIGHT PRINCESS
2005 - RE 4
2003 - WIND WAKER
2002 - METROID PRIME
GameRankings
2010 - GALAXY 2
2007 - GALAXY
2006 - TWILIGHT PRINCESS
2005 - RE 4
2003 - WIND WAKER
2002 - METROID PRIME
GameSpot
2013 - LINK BETWEEN WORLDS
2007 - GALAXY
2005 - RE 4
2003 - WIND WAKER
2002 - PRIME
Kotaku
2007 - GALAXY
Metacritic
2010 - GALAXY 2
2007 - GALAXY
2006 - TWILIGHT PRINCESS
2005 - RE 4
2003 - WIND WAKER
IGN
2013 - Last of Us
2012 - Journey
2011 - Portal 2
2010 - Mass Effect 2
2009 - Uncharted 2
2008 - Fallout 3
2007 - SUPER MARIO GALAXY (Wii)
2006 - OKAMI (PS2, Wii)
GT
2013 - Last of Us
2012 - XCOM
2011 - Uncharted 3
2010 - Mass Effect 2
2009 - COD: Modern Warefare 2
2008 - GTA IV
2007 - SUPER MARIO GALAXY (Wii)
2006 - TWILIGHT PRINCESS (Wii)
2005 - RESIDENT EVIL 4 (GameCube, Wii)
run away!