I actually defend this attitude to reviewing games (not finishing the whole thing) because it perhaps shows better what sort of game you're playing.
A good game will keep you playing to the end.
A bad game will not.
If someone criticised say Friends or Chuck or My Little Pony or some tv series they'd be allowed to after watching only a few episodes. The whole point of watching those few episodes is to give you an idea of whether you will like the series and if it is engaging enough to keep your attention until the end, but suddenly when it comes to videogames for some reason you have to play the whole thing to have a valid opinion? Sounds like more than a few people are just butthurt because their pet franchise just got insulted.
Also, I'm getting really bored of Dark Fantasy. It's like the nineties, when comic books sucked because people thought that the deconstruction of Alan Moore and Frank Miller could be best replicated by just swearing a lot and murdering people, entirely missing what actually made those books deconstructionist and good (see also Mark Millar, who is just mean spirited). Dark Fantasy can work, provided you understand what dark fantasy actually is, but most writers of it nowadays miss the deconstructionist satire of the genre, highlighting the flawed preconceptions of a legion raised on Tolkein, and just give us an entirely straightfaced Tolkein-esque fantasy with lots of swearing and shagging (see also BioWare)
As for the Witcher itself, I'm not a PC gamer, I'm not going to be a PC gamer, I didn't play the Witcher 1 and I'm not even remotely interested in the Witcher 2. As for this review it didn't make me laugh as much but I actually like that from Yahtzee sometimes because when his reviews don't make me laugh it's usually because he's making actual relevant points which will tell me whether I like the game or not, and not because he's a terminally unfunny halfwit who needs to be reminded that performing as a 'deliberately a snobbish tosser' and succeedding makes you look like a snobbish tosser (see also Jim Sterling)
And finally finally, I'm reminded of the Penny Arcade strip with this one.
http://www.penny-arcade.com/comic/2011/5/25/