While I rarely visit IGN, the reviews are of better quality than Kotaku's, but that's not saying a whole lot.
When I do look at reviews (rare), I try to read into the bulk of it, "de-spin" it, and ignore the score. I know that reviews are biased if not paid off entirely, especially when it's so easy for these publishers to cut off review copies, early interviews, early information (all the stuff that gets their site hits).
I'm not really defending any gaming site, but I definitely find Kotaku's reviews most laughable, with authors like this one writing many of the reviews. http://kotaku.com/5914348/three-words-i-said-to-the-man-i-defeated-in-gears-of-war-that-ill-never-say-again