You could make your argument a lot stronger next time by showing some comparisons to PS3, 360, and PC games that they were generous with.
If this is truly a bias against a single system then it would be reflected in the relative scores of the platforms not just the scores of the Wii. I could for instance make a review site where scores were from 0 to 10 and a 5 was considered average with 10 being absolute perfection. Giving a game like brawl or SMG a high 8 or a low 9 on that scale is a valid score. And it proves no bias against any console.
You have to show that comparison if you're going to yell "Bias!" or your voice will quickly get drowned out in a sea of fanboyism....actually now that I think about it that happens either way =P