I did some math and by the looks of it, the top 3 selling games worldwide from 15 to 22 December might very well be 3 Mario Games.
M&S @ Olympics, followed by SMG and ending with MP DS.
If it confirms Is this a first ever in the 21st century?
I think there were a couple of times this has happened in the past, over NES and SNES combined with GB and GBA. But I don't remember anything like it in the last 10 years...