I wonder if IGN will be grading graphics comparing them to the 360/PS3, or the potential of the system. But yeah, I agree with them about the scores they've given Sports, Trauma Center, and Monkey Ball. It's basic geometry, like watching snowmen bouncing around the screen. Zelda looks a helluva lot better.
Some reviewers at IGN seem to be reviewing graphics in comparison to the other next-gen systems. They weren't too fond of the stylized graphics in Wii Sports. It got only a 4.0.