Game of Thrones drew 4.2 million viewers in its first three showings on Sunday night, according to Variety.  There were 11 repeats in the first two days after the premiere, so that number will increase. 
The first showing of Game of Thrones drew 2.2 million viewers, between the first time views of True Blood (1.44 million) and Boardwalk Empire (4.81 million). 
HBO has renewed for a second season, two days after the premiere (see “New ‘A Game of Thrones’ Trailer” for a trailer).