Star Wars: The Force Unleashed, despite not really being such a good game (yes, I said it), has gone on to sell 7 million copies according to Lucasarts (via Industry Gamers). That's across all formats, though, which could potentially translate into one million copies for each. Either way, that's a lot of copies.
There's also a new DLC pack for the game out for both PSN and XLA today, which includes the new material previously only available in the so called "Sith Edition" of the game.