I've been think hard about what could be a good rating system. I came up with a mixture of the star and letter grade system(-/+). with a modifier(feelings).
Here are the ranks.
One Star
This game is beyond bad, to spend any time trying to comparing one star games, to give them a plus or minus will rot your brain. They are just bad, move along.
Two Star

or

These games have major flaws but there are some redeeming aspects. If your a fan of this genre, developer, series then give this a game a rent you might like it. No minus rating because if it's that close to a one star, it most likely is not worth saving.
Three Star


or

or
These games have some minor flaws, but overall they are good game. This is were the bulk of games will go, and it's not a bad things. Unless you totally dislike this type of game you should give it a try. Plus/Minus is for the reviewer to show if they game is closer to a two or a four but just not quite making it.
"It's barely a three or it's close to a four".
Four Star

or
This game's flaws are few, it is along the best games for it's system. This is a game that makes it worth buying the system it's on.
Five Star
This game is one of the best for this generation, even maybe of all time. To try and rank this game against other five star game is a disservice to this game and other games ranked the same. It stands among the few that will be remembered and played, years into the future. There is no 4star plus or 5star minus/plus, because it would become a pointless pissing match.
The modifier.How did you personal feel when done playing the game. Need more possible answers but among them could be. Short but to the point
Really enjoyed it.
Angry about the game.
Relief that it's over.