Reviews can be trustworthy, you just need to keep track on who writes them. When you always read reviews from the same people they can become trustworthy because you will know how their opinions compare to yours. That way you can put the review into perspective. It will not take long to find out witch reviewers are on the same line with your game taste. But also reading reviews from people you totally disagree with is helpful, you will know that if he doesn't like the game you probably will.
Being a (game)journalist myself for a couple of years, i can say that companies don't bribe reviewers to give good scores. However companies do make deals with magazines and websites for exclusivity. We had companies telling us that if you want to be the first to review their game, the score should be in line with what they have in mind. Specially for gamemagazines having a big game on the cover can lead to better sales, so in this way scores can be influenced from higher hands.
Although it can work the otherway around too, reviewers can press companies as well. One time a guy from the marketing department of a publisher told me that if i did not give their game the score in line with what they had in mind he would not send me copy for a early review. I told him that if it's going to work like that i would just buy the game myself at release and give it a low score on purpose. A few days later the game arrived with a note saying they hoped i would enjoy it. 
But these situation are a rare and most companies are very friendly and easy going with sending review material, no matter what score you give it. Of course big publisher are smart, they invite you on luxury trips and send you the game with nice goodies, trying to influence you into liking their game more. But i honestly believe most reviewers are honest with their opinion, although it does seem that a few to many are going along with the hype around a game.
What also happens a lot, is that reviewers only review games in a gerne they like in the first place, and when they review a game of a gerne they don't like their objectivity goes down the drain pretty fast. At the magazines/websites i worked for i always tried to find a good mix in reviewing games that are to my liking and that are not. And if i have doubts about my judgement i let my colleagues with a different taste than my own look at it, and agree together on what score to give.
People complain a lot about that the review system is broken, that reviews are unreliable and reviewers are only going along with the hype, but readers themself are also to blame for this. First of all most readers seem to forget that a review is an opinion. Good reviewers base their opinion on facts and not on personal taste, but it's still an opinion. Second is how readers interpret scores. These days a game scoring under a 9 is "bad", which is total nonsense. But somehow i feel this does influence reviewers to give score that are a bit higher than they should be. Because how can a reviewer make clear that a game is good and above avarange, but not top of the bill? A normal score for such a game would be between 70 and 90, above 90 is really exceptional. But because of the Metacritic culture that is going on, a game that gets a 75 is looked at as it had received a 40. So it would not surprise me if reviewers up their scores a bit just to make clear to readers that a game is good and above avarage.
If readers start to accept again that scores between 70 and 80 are very respectable, then maybe the scoring system will adjust again and the truly high scores will only be given to the games who deserve it.
