In a press releasing detailing full-year financials last night, Activision claimed it is now the biggest publisher in America, quoting NPD data. From here:
During the fiscal year, in the U.S., Activision grew its market share by 7.2% to a record 17.3%, was the #1 console and handheld software publisher in dollars, and had three top-10 best-selling titles in dollars overall according to The NPD Group.
For the fiscal year, Activision set an industry record for U.S. sell-through in dollars by a single publisher, according to The NPD Group.
The firm reported revenues of $2.9 billion for the fiscal year, as you can see here