As a general rule of my opinion the books are better because you can fit epic storylines into them while showing the thoughts and feelings of the characters.
A game has the advantage of involving its audience with its script more so than other mediums.
A comic book can show you and inform you. Words and pics are a great combo.
A movie can pull you into the action with its visual effects and sounds. Although a video game can do the same thing a movie allows you to sit back and enjoy the ride where a game requires your input and sometimes your frustration.
Check out the future Avengers movie that is based on a comic and will surely have a game.