Well there are 2 things to this argument.
For: Well, what you are reviewing is free material, and is freely distributed, as you are not modifying the engine in anyway, or breaking any other game terms that are limited, nor essentially 'Selling' a mod or scenario, you pass most copyright.
Against: You are paying to review a game that was distributed and sold for currency. Therefore the copyright stands against it as you are giving money on the game. Everything that is being reviewed is part of the game and therefore stands under game copyright. The reviewers are making money off of reviewing a copyrighted game and that should be against doing so.
I would avoid the matter entirely.