Don't think it should have an overly specific score. I actually prefer the Xplay scale of 5 stars.
5/5 is pretty much for everyone who has any interest in the genre.
4/5 is for everyone except maybe if you have specific tastes in that genre (so basically it gets a mode wrong like SP or MP)
3/5 is average and probably isn't earth-shattering for most but will entertain for its length
2/5 is only going to be liked by very few who really love specific things that the game does
1/5 basically no one will like