IMO don't worry too much about it, Edge magazine is a little weird nowadays.
For example they also rated the award winning Dragon Age: Origins a 5 out of 10.
But they aren't particularly harsh overall, they also contributed to the GTA IV and Halo 3 overhype with perfect 10/10 scores, two games which are good but clearly far from perfect.
For example in their minds a so-so game like PGR3 is worth a 9 and a much more fun racer like Motorstorm: Pacific Rift a 7...







