You should really use some sort of minimum number of votes or weighting system that applies to ratings. I mean seriously you have Alien at Rank 23 with 25 votes and Dialed In at 13 with 89 votes. These new games will always have hype and people will falsely drive the ratings up without some compensation method in place.

My $.02

15 is way too low, should be like 300+ or it should have a % adjustment. e.g.

1-50 votes (number)*.85
50-100 votes (number)*.90
100-200 votes (number)*.95
200-300 votes (number)*.975
300+ votes (number)

Simple and easy to implement. This would keep newly released games from pushing established and well liked machines down in ranking.

Rankings are fun to look at is all and having them skewed because the new hot game has a bunch of fanbois sucks.

As far as rare games go they probably shouldnt be ranked high anyway since not enough people have played one to balance out the lovers/haters. I don't think any system works for rare games.