I voted 'girl scout cookies' because there wasn't an option for 'it depends'.
I mean, one of the most arrogant things you can think of doing is playing a game for one hour, then declaring 'it's shit' as though it were fact; because obviously, one hour isn't enough to fully explore the game's world, its mechanics, its features, etc etc. It's like trashing a book ten pages in. The ball hasn't even got rolling yet. However, if you've played a game three quarters of the way through or even halfway, and then give up, there shouldn't be too much of a problem with that, because it really depends on content anyway: if the review's statements can be clearly led back to the game, it's no more invalid than anything else.
Example Time: I never finished Prince of Persia: Warrior Within. I only made it halfway. That is because I hated every second and I was lucky to even get that far. If anything, that shows that I thought it was so bad I couldn't even bring myself to finish it, which says a lot more in a review than what a witty insult ever will.
However, if I had to write a review on it, I think I'd be pretty qualified to do so. Even just making it halfway gave me more-than-sufficient knowledge on its characters, tone, cutscenes, graphics, sound, etc., which would be exactly the same even if I had decided to finish it. The only thing I wouldn't be able to fully comment on would be the story, because I hadn't seen it all the way through; but again, I had seen some of the plot, and would be able to make an educated guess on the rest of the story, e.g.: 'So far, Warrior Within has a lot of plot holes, due to its use of time travel; therefore, it hasn't been thought out very well, and I doubt that would change much by the end.'
So yeah, I could forgive Yahtzee for this. If anything, the Final Fantasy XIII review was pushing it. What was it, five hours, or something?