From my understanding Will Smith character is hardly even in the movie, so that would explain why it's not watchable.
I like this quote from a reviewer....
"You know you're in trouble when you find yourself feeling sorry for one of the world's wealthiest teenagers. And you're definitely in trouble when you wish the mess of a movie he stars in could be as entertainingly rotten as 'Battlefield Earth.'"
Smith is in the movie quite a bit, though he is not in any of the action, except for a brief scene close to the beginning of the film. Jaden does carry a lot of this movie-or drops it depending on how you feel about his performance.