Fallout 4's launch was a huge success. Bethesda announced today that the game shipped 12 million copies worldwide for launch day alone, "representing sales in excess of $750 million." In addition, the game is generating "record sales" at brick and mortar stores and across Xbox Live, PlayStation Network, and PC.
Developing...
http://www.gamespot.com/articles/fallout-4-ships-12-million-generates-750-million/1100-6432277/
// Mod Edit:
For comparison, Skyrim was 7 million for launch: http://www.neogaf.com/forum/showthread.php?t=452244
// Mod Edit 2:
Since some people are asking if this is an industry best record, Call of Duty: Ghosts shipped $1 billion worth on day one: http://www.ign.com/articles/2013/11/06/call-of-duty-ghosts-sells-1-billion-into-retail-in-24-hours
It is still quite high up there on the list of launches though.