I read GI, and it does seem to be somewhat biased aganst the Wii. Any Wii game review is laced with a healthy dose of weasel words. They tend to use them even when they give a good review resulting in a mixed message. Look for them, they are there.
They also do alot of...um...you know like when someone criticizes the president depite the fact that the topic they are discussing has nothing to do with the president, it's like that (forgive me for not knowing the technical term for this). They take these sort of left-field potshots at the wii frequently. The often make a point of comparing the graphics of the Wii to the PS3 and take this to the point where it annoys me. (Get over it guys, PS3 and 360 have vastly superior graphics than the Wii, I get it. Though I disagree about the margin. It's significant, but nowhere near as significant as it is often made out to be). Their reviews are often reminiscent of reading an editorial page in a newspaper.
I'd prefer to have an actual reference or two to illustrate my point, but alas I do not have one on hand.
I'll be happy to critique one of their reviews and point out exactly what I'm talking about whenever I get the chance if anybody is actually interested; as soon as I can that is.
I don't detect any GI bias towards the 360 or the PS3 for the most part. There probably is some as different people inevitably tend to pick favorites, myself included (any console that has Zelda).
By the way this sort of bias crops up all over the place and not just in game reviews. Just read any news article and at least half the time you'll see it if you know what to look for. And just because you might agree with the bias doesn't mean it isn't bias. It can't be stopped, it can't be reasoned with.
Damn, I just wasted like ten minutes of my life writing and editing this, go me. 
