No one is saying for them to just copy Wii sports, but the issue is understanding the values of the downmarket, and the ability to produce games that appeal to those values.
Unfortunately for Sony and MS, they lack the processes and values as companies to do that.
Nintendo is a gaming company, not a technology company or computer company, and a company with a very strong first party, in fact building its hardware around the needs of its first party, this is a major reason for why nintendo has the processes and values needed, and why Sony and MS are unlikely to be able to compete
Predictions:Sales of Wii Fit will surpass the combined sales of the Grand Theft Auto franchiseLifetime sales of Wii will surpass the combined sales of the entire Playstation family of consoles by 12/31/2015 Wii hardware sales will surpass the total hardware sales of the PS2 by 12/31/2010 Wii will have 50% marketshare or more by the end of 2008 (I was wrong!! It was a little over 48% only)Wii will surpass 45 Million in lifetime sales by the end of 2008 (I was wrong!! Nintendo Financials showed it fell slightly short of 45 million shipped by end of 2008)Wii will surpass 80 Million in lifetime sales by the end of 2009 (I was wrong!! Wii didn't even get to 70 Million)