As with all things in life, it's about balance. I have been more than happy to review other's code because I see it as more than just a critique. Often times it is also a learning opportunity by seeing their style or approach for example.

I have forced myself to be critical of my own code before others and try to keep it that way when it comes to reviews. There should be a standard of what to look for from language to language. This helps avoid style bike shedding with formats or naming.