Grey Carter said:
A review is an opinion, it is biased by its very nature. It's possible to make objective statements about technical issues such as "X runs better/has less bugs/has higher resolution textures than Y" but when you start talking about design or art issues, which make up the majority of a review - you're giving an opinion.
Not really, as you pointed out and I already said, you can do a review just pointing out what exists. Games are very detailed, so theres a lot to talk about. Even when covering art issues, you can still make objective points, it's really the way you word it.
People keep saying this is impossible, and I find that as silly as fanboy's comparing quality through sales and the majority. When you become really good at something, you'll notice at how ignorant most people are when you discuss that specific thing you're good at. This goes for every hobbie and job (not for most people unfortunately). It's a state of mind to be biased and it can be controlled.