You put too much stock in reviews. The games pretty damn good so far.
In any case, 8 reviews is hardly anything. You shouldn't be making topics like this until a game has 20-30 reviews in GR.
Also keep in mind that the Sonic Adventure titles didn't age very well. Theres a reason reviews keep saying that the 2D titles are far better then the 3D title. The Adventure titles where good for their time, but if they where released the same day as Sonic Rush Adventure with up to date graphics, they'd recieve 6s and 7s. These games where released a long time ago, and their scores cannot be directly compared to scores of the newer games, because standards change with time. SA2:B on the Gamecube averaged in the low 7s, released just 9 months later with improved graphics and a few additional features. If anything, the Adventure titles where overrated, even in their day.
80% is good for a Sonic game regardless, I disagree with your notion that just because it's Sonic, it should score in the high 8s and 9s. We can't expect a Sonic game like that for a couple more years, BioWare RPG aside. The franchise has a lot of kinks to work out.
