Honestly, Yahtzee has given out how many completely positive reviews? He likes some games, sure, but he almost always says something bad about it. That being said, I'm at school, so I can't watch the Halo Wars one just yet.
That's becuase Yahtzee's job is to find problems and make fun of them. That's the whole point behind his videos, it's to find even the smallest flaws and then go off on a colorful obscenity laden rant about them. It's the whole basis for his humor. Just like the Angry Video Game Nerd. AVGN actually had a video where he explained that, no he doesn't hate every game that he plays, he knows the things he complains about aren't that big a deal, but he's playing a character and that's the basis for he comedy.
I take Zero Punctuation as less of a review, and more of entertainment
It was funny....except for the part where he mentioned halo's fan base being a bunch of dog F#@*ers, then made fun of the 14 year old canadian boy in ontario that ran away from home after his parents took away his XBOX...poor kid got lost and tried to climb a tree to look find a way home, fell out and was found dead...a little too far dont you think?