A lot of reviewers feel this way, but they end seeming like everyone else in the crowd.
For me, I do reviews on my blog because I feel that is where I can deliver my views, just like AstroNerdBoy and MagicBox.
The choice is all yours though, so I understand your reasoning.
Many people are like this when they start writing, all I can tell you is just to find something that is right for you and what you want to focus on.
For me, I look for things that make stories much more interesting or enjoyable, and then what detracts from it and why.
Some people might not like it, but it gets my points across and allows me to express how I really feel about a work, and has been able to help one writer get better.