I noticed the following comments in a recent issue of People Magazine - in an article on summer stinkers in the movie business:
Why The Last Airbender didn't work: Bad acting, lame visuals, and a script that bends logic.
Why The Killers didn't work: The actors had no chemistry - and painful jokes.
Why Jonah Hex didn't work: The holes in the script are bigger than the one in Hex's face.
Notice the common denominator: bad script, bad jokes, bad script.
You can have the best actors in the world, but if the script isn't right, the movie will never work.
Want to know more about writing scripts that work? Check out http://www.screenwritingu.com. Good people there.