Back when Gamefaqs still had a lot of people doing user reviews, I used to read a lot of the longer ones, kind of comparing between the really high, the really low, and the really mediocre scoring reviews. You could usually piece together a pretty accurate picture of the game by doing that. These days, though, it seems like nobody bothers to write up any reviews on Gamefaqs anymore, and I've never liked the user reviews on other sites. They tend to be way too short, just a paragraph or two long. Gamefaqs reviewers always broke it down into somewhere between five and ten categories, each getting at least a paragraph of explanation.
So what do I do these days? I basically ignore reviews entirely, going on positive word of mouth instead. Basically, I'm more likely to trust someone who gushes about a game outside the context of a review than I am someone who is specifically setting out to review it. That's true whether they're a pro (advertising money, much?) or just some random schlub.