Downvoting

No, such a thing doesn't currently exist. It's unlikely that something like that would be added, as what games people enjoy is a rather subjective thing. I could see people easily abusing it and going on a down-voting spree against a specific category, fandom, or person that they happen to dislike.

As it stands right now, vote scores get reset every month, and like counts remain.

The possibility of leaving site reviews is something that I've been thinking about though.