Looks like NSMB Wii will be the fastest to 15 million at 32 weeks

[Bruno Muñoz]

Week	Americas	Japan	EMEAA	Worldwide
1	985,340	943,582	361,427	2,290,349
2	605,461	454,233	372,729	1,432,423
3	465,534	549,756	421,960	1,437,250
4	580,675	510,745	399,425	1,490,845
5	735,863	288,554	440,634	1,465,051
6	838,835	148,182	446,348	1,433,365

New Super Mario Bros Wii (first six weeks)

This is the most impressive feat ever. I think it will be almost impossible to break this record.