Attempting use ranks like this as indicators of quality is about as stupid as you can get.
I would agree there but then again I think giving grades to games in general is pretty damn stupid. It's an exercise in laziness, that way we don't need to read the text, we can just look at the score and since we have Metacritic, we don't need to read anything anymore because 50 or so journalists atributed it an arbitrary score. That's bad for everything involved.
To be perfectly fair, this system works to point out those awful bug filled pieces of shit, like THPS 5, and the games that are truly masterpieces and define their generation, like Uncharted 2 or Super Mario Galaxy. For the middle ground, games that are between 90 and 60 or so, I tend to think it's all in the same category: try it out because it works and should be fun. Whether it has a green score or a yellow score is a bit elitist.
I like how Eurogamer does it for instance with their own scale, and I loved how Joystiq reviewed the games with as little negativity as possible, and very much enjoy reading Jim Sterling writing weird funny shit. Besides those, gaming journalism right now usually is a bit too negative and a bit too enamored with itself and I'm not a fan of that.