I really liked the Ludumdare karma system. Taking the number of your ratings vs the number of ratings you got, with games below 20 rating getting preferential treatment. They also gave heavy emphasis on comments to boost your placement. All this was shoved in some formula to determine the order of games and I must say it worked quite well.
They did write that they will keep an eye out for cheaters, but it's not like it was too clear on what they do or how they do it (which is understandable). Now that I look at my LD page, they specifically write karma for feedback, so that would imply you only give a boost from your comment if the creator liked it. That would actually be pretty darn great! You would have to tell the peps to only like helpful comments and not like the the "nice game rate mine plz" and it would instantly curb the issue.