Game reviews, or any reviews for that matter are a hard thing to justify. There are many reasons for this, and I will go over some.
One big reason, which I will get out of the way now, is personal opinion. This one alone should make people wary of trusting any reviewers, even ones that often have similar tastes. By the mater of nature, we all are different, it's in what we like to eat, our favorite colors, what music we listen to, we all have different tastes, it's just human nature.
So why then, do so many people seem to just listen to reviews, without thinking or experiencing it for themselves? It seems like often times, people are too eager to follow the bandwagon, not letting themselves enjoy what they personally enjoy.
Another reason that reviews shouldn't be taken for truth is the concept of what makes a 'good' game without personal opinions. Some would say it is the compilation of good game mechanics, good level design and graphics. Some would say it's all about the music and story.
Following this, without taking personal opinion into account, should a 'good' game be fun to everyone? If not, then what does it mean by 'good game'? A well put together package? If so, I hardly see reviews being taken as anything more then a footprint to show what a game might be, not a formal description of what to expect in terms of quality of fun.
Reviews often rate different parts of a game, Graphics, Sound, Gameplay, ect. This would mean that a game cannot be good without these categories. However, sometimes there are games that will inevitably fall into low scores in all the categories, yet be a good game, so what are the scores for?
And why numbers? What do they mean? Sure you can say a 9/10 means the reviewer is rating it a nine out of ten, which is a good score. Now look deeper, what does a 10 mean? A perfect game? Some people think that, and others don't which makes drawing any kind of comparisons with reviews quite impossible. Finally, what equals a rating? Should 5 be average? If not, then what is the point of all the numbers that low. Generally, you see reviews give even 'pretty awful' games fives and sixes, which makes the point of having any lower numbers very small. Sure you could run into a game once in a while that deserves it, but it makes it that much harder to tell which games are good or not, as the rating system is more like 1-5, and even then the ratings usually land in the 7-10 range, making it hard to really see a point in the numbers.
So are reviews worthless? Maybe, depends on your definition of 'worthless'. I believe they should not make up your mind for you, but perhaps guide you to understand what the game is like, not to give you and ending opinion on the game.
"Jon God, you are being hypocritical! You review reviews yourself!"
This is true, but I don't write them to convince people of anything. Instead I try to write them as a guide to what the game is like, giving good and bad parts about it, along with number scores, for those that can't go without them, then finally having a "Overall Fun" Score which really is how much fun I PERSONALLY had with the game, and not a overall score out of the list on numbers, or the listed good and bad things about it.
It's up to you to get what you want out of what you read, but I implore you to look beyond letting reviews make up your mind, and really play what you enjoy. Don't worry if it's reviewed harshly. If you do this, you will get more out of your gaming experience.