Why is it that whenever an individual disagrees with Yahtzee's assessment of a game - or his methods - they fall back into the same old rhetoric about these being entertainment pieces instead of actual reviews? In what way is an opinion piece, or something that is in some way humorous, not a valid review? If we are to hold games up to the same standards we do film and literature, then we should abandon this silly notion that game reviews require this objective, removed, scientific analysis complete with pointless numerical score. An impression is still a useful tool, and you should never use a single review as an excuse to buy or not buy a game. Instead, think about how the reviewer experienced the game; think about your relationship with that reviewer, what their interests are, how they approach games, and how that differs from or is similar to your own. When you read (or in this case watch) a critic's work for a long enough period of time, you understand how similar to your different from your own preferences they stand. This is the true benefit you gain from a review, not an 88.3/100.
I'd never claim to speak for Yahtzee, but in my opinion, his reviews are every bit as valuable and legitimate as any. More so, even, than most reviews from major publications, where you're constantly wondering what the critic's relationship with the advertiser is, or what kind of editorial pressure they might be under to deliver higher scores in order to stay afloat.
Yes, they have the added benefit of being entertaining, and yes he most certainly doesn't present every possible angle for you to consider, but that's the thing about art - it's a personal experience. Why should anyone bother to try to fight through dozens of hours to find a way to enjoy something that clearly does nothing for them when there's so much more out there that does, or might? There's not enough time in the world to play every game, read every book and watch every movie.
And to echo other posters here, I imagine that I might like The Witcher for many of the reasons Yahtzee doesn't. I may not. There's no telling until I get the opportunity to play it. But my enjoyment of the game wouldn't change how I feel about game reviews any more than this post will prevent another few dozen people from posting about how they only watch ZP for laughs.