I have something of a problem with reviews at the best of times. Because taste is such a subjective thing, I found a long time ago that most film reviews were of limited use to me. Eventually, the approach I found worked was to find someone with broadly similar tastes to my own, and then trust what that person said. That was reasonably reliable, but not totally.
However, it's in the field of game reviews that I've really started to see some problems. In particular, I have a big issue with game reviews that come out prior to the release of RPG products. There are several issues with this, which I shall state in question form:
Have you even read the thing? This is a big, big question that leaps to mind, especially with RPG reviews. Very often, these are very large, hardback tomes. And there are no full-time RPG reviewers - everyone who does that job must necessarily fit it around the rest of their lives. That means that actually reading the books, a prerequisite for doing a decent review, takes time, and a significant amount of it. Actually digesting the material and giving it some thought takes yet more time.
But then...
Have you played it? Actually, this is probably the bigger issue. An awful lot of games play out differently from the way they read, some better, some worse. So merely reading the rules (or adventure, or whatever) is actually quite a poor guide to quality. And, sure enough, that takes yet more time.
When you played it, did you play it as-is? I've played "Arkham Horror" all of once, and I thoroughly enjoyed it. But I'm in no position to review the game - I know fine well that the game we played was not the game as presented in the rules. There's good reason for that, and those changes are no bad thing... but they do render any review I might do invalid - my experience will not be your experience.
So it is with many RPGs, and especially adventures - there are very often significant flaws in the material that a DM will simply adapt for. This can give rise to a good experience... for that group. But "you can fix it" doesn't mean "it's flawless".
What are your biases? This is a big one. And, in RPGs, it pretty much renders reviews useless. Fact is, we've just come out of some very nasty Edition Wars (and, indeed, they may well still be ongoing in some parts). This means that any review of a D&D product may well be written by a D&D fanboi, determined to present only the absolute best side of 'his' game, or might equally be written by a D&D hater, determined to present the opposite. And likewise for Pathfinder products. (Worst of all, many of our biases are unconscious - it's entirely possible that someone could set out to do a fair review and yet be literally incapable of seeing things that don't fit his biases - just as some Rangers or Celtic fans are literally incapable of seeing the good in the 'other' side.)
Anything to declare? If you received a free copy of the game, you are not in a position to rate it based on "value for money". You're dividing by zero.
Conclusion:
The whole topic is a tricky one. Reviews clearly aren't useless, and yet pretty much every review is questionable in some regard, and probably multiple counts. In theory, something like Metacritic might be worthwhile, in that lots of reviews can be aggregated and some sort of average arrived at then... but Metacritic is known to be badly flawed itself in at least two ways. (And, besides, there aren't huge numbers of RPG reviews out there from which to do such an aggregation.)
So... caveat emptor, I guess.
And, yes, I am still going to do the occasional review on the blog. And it will be exactly as flawed as every other review, mostly failing on the "have you played it" question.