Total worldwide sales: 81.99M
How'd they do it? Wii Sports's record-breaking success is owed in no small part to the fact it was bundled with the Wii console in every region but Japan when it launched in 2006. It also helps that it offered the first taste of Nintendo's then-revolutionary motion controlled gaming console and its new Mii online avatar feature, making it a hot commodity for Nintendo fans who had been chomping at the bit for the Wii's arrival.
Born of Nintendo's desire to dominate the casual market, and delivered on the wings of media hype, Wii Sports bridged the gap between traditional gamers and the so-called “non-gaming public” in a way no title had done before. It presented fun-loving consumers of every age a family-friendly experience that could be picked up and played by anyone with a living room and reasonable mobility. This mass appeal earned it an endorsement amongst critics and a starring role in living rooms, dorms, rec centers, and senior citizen homes across the globe. It's lasting popularity led to a 2009 sequel, Wii Sports Resorts; and a 2013 Wii U remake, Wii Sports Club, featuring HD versions of the five original sports: baseball, bowling, boxing, golf, and tennis.
Because it came bundled in a insanely popular Nintendo console in most countries outside of Japan, we're not counting it as its own game.