reviews are opinions and i'd say you would have to find a balance between "blindly" believing in a score to rate a game vs reading into why those reviewers found the game good or otherwise. what matters a lot to some gamers might mean nothing to another (Eg. HD vs non-HD)

personally i found i tend to agree with views of Matt Cassamasina of IGN (now he's with Apple). so i would trust his reviews more than others. i'm sure after a while you'll be able to judge whose opinion matters more to you