Wii comparisons: At 21 weeks, Wii is where GCN was at 83.3 weeks (April 14, 2003), DS was at 21.0 weeks (April 23, 2005), where PS2 was at 18.9 weeks (July 8, 2000), and where PSP was at 51.3 weeks (November 29, 2005).
PS3 comparisons: At 24 weeks, PS3 is where PS2 was at 2.9 weeks (March 18, 2000), where PSP was at 10.1 weeks (February 13, 2005), where GCN was at 15.4 weeks (December 25, 2001), and where Wii was at 4.3 weeks (December 25, 2006).
PS3 vs Wii: Weekly shares were 12.4 / 87.7, Wii besting last week's percentage of 86.4 but still slightly below launch week's 91.8. LTD shares are now 28.1 / 71.9. If Wii stopped selling and PS3 continued at this rate, it would catch up in 119.9 weeks (August 8, 2009). If "the flip" occurred, the systems would meet up in 19.7 weeks (September 6, 2007).
(Now Wii has done 600% more than PS3.)