http://vgchartz.com/hwlaunch.php?cons1=PS2®1=All&cons2=XB®2=All&cons3=GC®3=All&weeks=400&weekly=1
It's hard to tell from the above graph. The PS2 did have a higher spike of 1,326,373 for a Christmas week in 2005 (WE Dec 24 2005) than a spike of 929,897 in 2004 (WE Dec 18 2004).
Using Hardware by Date, the PS2 sold:
18,453,863 in 2005 (WE Jan 01 2005 to Dec 31 2005)
15,909,309 in 2004 (WE Jan 03 2004 to Jan 01 2005)
19,015,858 in 2003 (WE Jan 04 2003 to Jan 03 2004)
21,434,573 in 2002 (WE Jan 05 2002 to Jan 04 2003) - Peak year
I find it quite interesting that the fiscal numbers differ so much from the calendar periods. I always thought the first calendar quarter wasn't significant, but it looks like the sales of the slim continued into Q1 2005, as shown in the first graph, causing the discrepancy.
I have not crunched the numbers in as much detail as the PS2, but the other systems to not seem to show signs of a second peak.
What do you think would cause the Wii to have another peak? So far Nintendo has not discussed a slim redesign like the PS2 had. New colours? New software? New bundles?