The Force Unleashed apparently sold 1 million copies during its first week of sale. I would think this is considered a success thought not necessarily a home run considering Halo 3 sold 4.2 million units in it's first week and Grand Theft Auto IV sold 6 million. If I'm not mistaken, both of those games were released for the Xbox 360 exclusively whereas The Force Unleashed was released on virtually every platform except for the PC. Xbox 360 versions sold the most whereas the rest of the sales were pretty evenly distributed between the rest of the platforms. It's safe to say that Star Wars is still alive and well in the video game world and I would expect TFU to be a game that lingers on the charts as die hard fans eventually pick up multiple versions of the game to get all of the content from multiplayer to exclusive levels.
Please note that this is based on the preliminary numbers of Vgchartz. Well let you know when official numbers are released.