Seems like this topic has been brought up as people want to compare the Switch to various previous launches. Thoguht I'd comb around and see what other data I could find. Kinda fun to peek back at past systems, here's what I have for first month sales in the US:
PS4 - 1138k (Nov. 15, 2013)
XBox One - 909k (Nov. 22, 2013)
Game Boy Advance - 880,784 (June 11, 2001)
XBox Original - 722,177 (Nov. 15, 2001)
GameCube - 662,560 (Nov. 18, 2001)
Sony PSP - 620,000 (Mar. 24 2005) *source on this is iffy
Playstation 2 - 500,000 in first weekend (Oct. 26, 2000)
Sega Dreamcast - 514,000 in first 2 weeks (Sept. 9, 1999)
Nintendo DS - 479,000 (Nov 21, 2004)
Wii - 475,000 (Nov 19, 2006)
Wii U - 425,000 (Nov 18, 2012)
Nintendo 3DS - Just Under 400k; 440k in 1 week (Mar. 27, 2011)
Nintendo 64 - 326,000 in 2 days (Sept. 29th, 1996)
XBox 360 - 326,000 (Nov. 22, 2005)
Playstation 3 - 187,000 (Nov. 17, 2006)
Bonus data: For September 1996 (two days worth of sales) the two N64 launch titles sold as follows: Super Mario 64 (282,000) for no.1 on the month and Pilotwings 64 sold 85,000, good for no.4 that month.
Looking back on it, GBA, GCN, and the original XBox had really good launches. Nintendo has definitely been undershipping launch hardware since the GameCube.
PS4 and XBox One launches were ridiculous. If anyone has launch sales for Playstation 1 or SNES that'd be great. I think the Console Wars book has some data for the SNES early days, I'll have to look over it again.
