Tthree, that all depends on your outlook on a movie. I can not enjoy any action movie starring guys like Arnold Schwarzenegger or Sylvester Stallone because the first time they pull out a bow and arrow and wipe out 32 guys with machine guns or take a 22 and completely blow up and destroy an armored car, it is just more than I can take.
If you can watch "21" just for the story and not worry about picking it apart because of accuracy, then you'll probably enjoy it. Otherwise it most likely isn't for you.
Bookmarks