If the game is imperfect a 6.5 is an above average score. The only reason people get upset about 6s and 7s is they think a 10 point scale is like a grade school A,B,C,D,F. It's not. 5 would be a mediocre game, 6 would be better than average, 7 would be good, 8 would be great, 9 would be stellar, 10 would be an extremely rare perfect game with no flaws. Everything below 5 would be different shades of suck, but anything above 5 would be worth playing depending on a persons tastes.
Zelda SS is a 7 in my opinion. Gravity Rush is probably a legitimate 6. People need to stop getting all worked about about meta scores and .5s. And most of all the vast majority of gaming review websites need to use their entire 10 point grading system instead of just the top and bottom three numbers. It drives me crazy that truly shit games get 1-3 and mediocre to amazing games get 7-9 when the majority of games are really 4-6. There are so few perfect 10s that it should be shocking when a game scores it. The only game I've played in the last decade that I'd consider a 10 would be Portal 2 and that's because I prefer shorter games that can be enjoyed in small sessions.
I highly doubt Gravity Rush is the as good as Portal 2, but it also looks better than your average bargain bin game so 6.5 seems about right to me.