I'm not a fan of the series either, yet the reviews of GTA4 seem more biased (they both seem biased anyway).
It's like with other reviewers and Brawl. GameInformer didn't like it and thought it took "no skill" and was just "pushing random buttons" (which is total bullshit) and they gave it a 9.5 when it deserved a 10. They kept knocking it just because it sold better than a lot of core games for a while.
They (GI) also gave NMH a 6, and knocked every part of the game down just because they didn't like it or it was "too hard" or "subject matter... may offend". Bullfuckinshit. I don't believe reviews are really worth anything anymore.
So there. It's not just MGS. Many Reviewers do it to every game that isn't "Core", because they want to keep the "core" gamers happy. I mean seriously, who gives Wii Fit an 8 just because they don't personally like the idea and the "casual market"?
Also, I swear someone's just giving out all these 10's just to kick OoT off of it's [proper] throne.