On a Mario Kart note, I think the most impressive example of holiday sales and boosts is shown by Mario Kart 64 9 years ago. MK DS was released about 4-5 days earlier than MK 64 was, but if it can show the same kind of bounce in weeks 2-4 then it'll do well:
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Mario Kart 64 N64 Nintendo 16/12/96 328,750 328,750
Mario Kart 64 N64 Nintendo 23/12/96 394,750 723,500
Mario Kart 64 N64 Nintendo 30/12/96 220,500 944,000
Mario Kart 64 N64 Nintendo 06/01/97 183,750 1,127,750
Mario Kart 64 N64 Nintendo 13/01/97 69,500 1,197,250
Mario Kart 64 N64 Nintendo 20/01/97 42,500 1,239,750
Mario Kart 64 N64 Nintendo 27/01/97 27,250 1,267,000