
It's an open secret, really. Most big publisher's reviews are rushed and overrated, and the reviewing sites and magazines have good financial reasons to do so. As a consequence, I wouldn't pay attention to any review with gives out 90% or more to any game which just came out. After two or three patches and an expansion - maybe. But on release date? No way in hell.
Hmmm, the problem is, people expect the reviews to be posted by the release of the game so they can use them as a guide on whether they'll enjoy the game or not. By a week or two later, you can just find out from friends or other players on the Internet. Nobody reviews game *patches* (well, ok, sometimes they'll do a second article if a noteworthy patch that really fixes a lot of problems comes out).
So, they review the game as it exists in their pre-release review copies. They have to make a certain assumption, when reviewing games, that some of the worst bugs and problems are going to be fixed in a post-release patch, though they also usually disclose those problems to their readers, then rate the game on what they think the game experience will be when those problems are fixed. That's just the nature of the beast - it's the most reasonable way to go about it, and the expectation is that people who buy the game on release day know there will be some issues which will be addressed later and can live with that.