Well, this sums up pretty well that whenever I write reviews I never give ratings (unless I'm writing a review on a website on a website requiring me to). When I review I try to be informative and although I do give my personal opinions in a review (no escaping that) I try to prefer to focus on facts as much as possible. Ratings are too vague and indeed it's hard to say what a certain number of stars mean. But I guess no rating system either a star system (1-5) or a point system (1-10) or just "like"/"dislike", will ever work out properly.
When it comes to rating system on sites like these, I guess it could make sense for myself if games are recommended based on my rating behavior. If I'd only give RPG games a high rating then that I only get RPGs in my recommendations or something silly like that. But that will sometimes also work counterproductive, as there are games out there pretty unique and which I really just stumbled upon and tried and liked and is unlike anything I ever expected. Hey, with YouTube videos I've encountered the same thing. So here too ratings can work against me.
Now in my opinion the best rating system is no rating system at all. But that's my personal opinion.