People used to say the same about mountain running, where it was mainly European runners winning, but take a look at the results over the years...
http://www.wmra.ch/index.php?option=com_content&task=view&id=564&Itemid=34
World Mountain Running Trophy/Championship, Men's Individual champions:
2001 - DE GASPERI Marco ITA
2002 - WYATT Jonathan NZL
2003 - DE GASPERI Marco ITA
2004 - WYATT Jonathan NZL
2005 - WYATT Jonathan NZL
2006 - ORTIZ Rolando COL
2007 - DE GASPERI Marco ITA
2008 - WYATT Jonathan NZL
2009 - Geoffrey KUSURO UGA
2010 - GASHAZGHI Samson K. ERI
In 2010, East African runners took the first 6 places. Most likely a matter of time for ultras too, but why train half a year for an ultra, when you can get start money to run a big city marathon?
The 100km world record is held by a Japanese guy with a 2:10 marathon PB.
http://www.iaaf.org/statistics/toplists/inout=o/age=n/season=0/sex=M/all=y/legal=A/disc=100K/detail.html
Watch out if Gebrselassie ever decides he wants the 100km record to add to his collection.
To answer the question - football, a.k.a. association football, a.k.a. soccer.