I used to read reviews more than I do these days, but then again the amount of product that I'm buying is also less than it used to be. Basically I'm at the point where I've got such a short list, I've usually made up my mind to buy it already.
I mean, I'm buying Buffy sight-unseen. It could be crap, but I doubt it for two reasons:
1) I like Buffy, and,
2) I have the other Unisystem games, and like them, so the system isn't an unknown quantity.
In that sort of case, I don't need a review. Same with the system block basics of D&D. If I want the official rules for Deities and Demigods, or for Epic Level play, I have to buy those rulesets so it really doesn't matter what's in them unless they are grossly, terribly done (and that comes down the grapevine pretty quick). I only read reviews for something I'm curious about, but don't know much about, but want to do some checking before I spend what little money I have.
While ranty reviews (either in the good way, when I agree, or in the bad way, when I don't agree - yes, entirely subjective), can be fun to read but in the end, IMO, are useless. They are hideously biased one way or the other and aren't going to give you a clear picture of the product.
For me, a good review is objective. Yes, this is also subjective, but by this I mean the author can write a review and do two things (Today's post is brought to you by the number 2!):
1) Keep his or her snide comments to themselves.
2) Look at a product and see how it could be used by all sorts of gamers and for all sorts of playstyles, not just his or her own.
For example - I'm no fan of Rolemaster (too many charts for me), but this is a game that will appeal to a gamer who likes loads of detail and a fairly deep ruleset. If the author of the review simply says it's too complicated, all he is telling me is that it is too complicated for him. Show me how complicated it is, and I will judge whether or not it's too complicated *for me* based on what you describe.
I also expect, if it's a review of a game system, discussion of both the setting and the system. I want the basics of how the game works, how detailed chargen is, and a brief overview of the setting. Giving me one or the other tells me only half the story. And if it's a review of a product, I want to know what I can do with this product and what it's purpose is supposed to be.
I think it is possible to dislike a product, and still write a review that can help a consumer to make up his or her mind about whether or not it would be useful and/or enjoyable to them. I don't see them very often, but when I find them, I'll keep going back to the same reviewer in the future for more reviews.