Some people know how to promote their game in the community forums and get dozens of ratings and comments, which has nothing to do with game design... As long as a game has more ratings than the median, it feels right to me to consider their score valid.
To me, voting shouldn't be public.
There could even be an option for a dev to be presented a random game to rate, and that rating could have more weight than non random ones, that way you ensure fair rating.