I like to think of Yahtzee's reveiws more as stand-up comedy routines than actual feedback, since the only things he's EVER given positive reveiws to are the classic games that every single person on this planet without some sort of labotomy owns and loves (Prince of Persia, Silent Hill 2, e.t.c).
And the games to which he assigns astoundingly negative reviews are the ones most of us can recognize as shit and likely weren't gonna get anyways, like Sonic #108 and Tomb Raider #792.
Would I buy a game because he recomended it? No, but I might take a closer look at it if I've heard other good things. Would I deter myself from buying a game because he bashed it? No because he bashes essentially everything. It's his entertainment niche and there's nothing wrong with that, on the contrary, human beings like to see people or franchises getting bashed and taking falls. (Accept your nature, join us on the dark side *sith lightning*.)