The analyst firm is claiming 300,000 G1 handsets were sold in the US between October and December 2008, compared to 1.75m iPhones in the same period, which is about 5.9 times more.
Although the analysts issued no worldwide figures, it's thought Apple's iPhone will still have sold more devices, as its available in 70 countries as well as the US. The G1 is currently only available to UK and US residents.
However, Morgan Stanley analyst Kathryn Huberty says that outside of the mobile phone market, Apple isn't performing as well as expected. Sales of Macs are thought to have grown by 4 percent compared to last year, but that's below the 10 percent growth estimated for the PC market as a whole.