Sales after 2 days for MH4 (for the week for 3DS)
MH4: 1.875m
3DS: 298k
http://www.famitsu.com/news/201309/18040182.html
3DS sales Comparison (via NeoGAF):
3DS Peak Holiday 2011 - 510,629
3DS Peak Holiday 2012 - 433,788
3DS Launch - 371,326
Monster Hunter 4 Release - >298,000
3DS LL Launch - 235,974
3DS Price Cut - 214,821