It's funny that the first answer you received is a link to a game. Seems like that guy didn't even bother to read the first two lines of your post.
Anyway, we are exactly in the same situation, I left tons of comments and yet I'm still below 20 ratings (did not think to leave a comment for a couple of games at first, I'm new to game jams, but then I understood that's important).
As soon as I get to 20 I will start sorting games by "most karma" and look for those that are close to the top of the list but still below 20 ratings, so at least my votes will go to someone that really deserves an extra rating.