Plain and simple.

Bale has hits behind them, but MOST of the time he was NOT the driving force behind those hits. I don't mean he gives a weak performance--usually the opposite. I mean he is never the selling point of the movie.

I don't remember hearing "CHRISTIAN BALE IS..THE DARK KNIGHT."

And most people still haven't heard of Hard Times and The Machinist.

Johnny Depp, though? You can basically just put up a movie poster with his picture on it and no title, looking crazy and mysterious, along with some random date: 2-14-10.

People would get excited.

Plus Depp's performances are insane. Even when they aren't amazing, they're interesting. I mean look at Once Upon a Time in Mexcio. He had a relatively minor role in a sub-par movie, and he made it easily the best part of the movie. He might as well have been the star.

Too bad for Bale, but come on. He always comes with strong acting, but, that I've seen, he doesn't or hasn't yet given the kind of performance that steals away the movie.