First of all video games require imagination. Most movies needs little to no imagination and books are usually very good to describe what happens and what characters think. Roger Ebert calls it authorial control.
Video games require imagination because you take on a character and you are that character throughout the game, whatever game that may be; It could be a soldier in Battlefield 2 or the purple tentacle from the 'Day of the Tentacle'.
You need imagination to put yourself in the situation of which the game puts your character. Therefore video games should be treated differently from movies and books. A good computer game like Full Throttle is an experience no movie or book provides and I alone for that fact consider many games to be art. To me it's a computer game work of art and you need imagination to live it.
I can see it must be hard for Roger Ebert to fancy video games and do proper research because he's not that kind of person. He might have some imagination, but I doubt it's enough to enjoy video games as most people do on the Shack.