I don't like the way review scores work, but 6.5 is certainly not good. Sadly in the 10 point system is very much used in most places like a grading school system. You can basically look at the points as letter grades..

9-10 = A
8-8.9= B
7-7.9= C
6-6.9= D
5.9 and Under = F (basically different degree's of suck)

An average game with flaws usually scores in the 7 range. A good game within 8s..an exceptional game in the 9s.

6.5...it's not quite a complete failure but theres enough wrong to ensure than only a select few would enjoy such a title. Usually hardcore genre or series fanboys only enjoy it.