To be honest, I like that he is so difficult to please; because I am much the same - like him, I'm an old-gen gamer, and have seen a lot of the best and worst gaming has had to offer since they got popular; and to tell the truth, a lot of the time I can say, "they don't make them like they used to".
Back in the day lack of resources and technological constraints forced game designers to be innovative and create far more colorful game mechanics that would make playing the game more immersive and involving. These days, a lot of games just try to be immersive in its graphics, special effects or sound or voice-acting... which is all well and good, but it is so easy to just get lost in that and end up with what seems to be an Avatar computer game (really pretty looking, colorful yet pointless and not exactly gripping). I can watch a DVD movie or such for that because a lot of games can even do without the 'game' part and just jump straight into the cutscenes and pretty things to look at. Gaming is kind of dying from cookie-cutter mechanics and gameplay.
When Yahtzee is reviewing a game, he's not just looking for an 'ok' or 'good' game, or game with just really nice graphics or lots of shooting action and 5 million guns, he's really looking for a polished, working, mind blowing piece of art. Without him and reviewers like him, I don't think game companies feel threatened enough to pull their socks up and keep churning out more awful games.
At the end of the day, grain of salt or not, I don't think anyone actually WORSHIPS him as some people may suggest to follow every one of Yahtzee's words to the letter - we are of course entitled to our own opinions, and have our own preferences. I mean, regardless of what he may say about the Mass Effect series, I would still get the next instalment to see where the story goes - sure I'll probably do away with the combat because it is still very uninspired, but the rest is intriguing enough for me to look into it.
But if Yahtzee says something is good - I think it's worth at least finding out why.