Much as it pains me to say it, I think ultimate-guitar's rating system is solid. I forget the exact number, but a tab has to be rated a minimum of X times before the rating even shows up. I'm sure someone else mentioned this in the various threads we've started on the subject, and chances are that I poo-pooed it in the past, but we don't have a lot of other options.
Speaking of UG, I got tired of users there stealing my tabs from here, so lately I've been submitting my BBT tabs over there. I've also filled a few requests there – but only after submitting them here first.
Anyway, back to the ratings. Right now, comments are only required if a user rates a tab lower than 5 stars. And that worked for a while, but now people just rate everything five stars to avoid having to leave a comment. But if we were to require a comment for every rating, good or bad, that could help. Also, maybe show every user that rated a given tab, along with the rating they gave it. I have a sneaking suspicion that if we were able to see who's been rating new tabs over the last several months, a whoooooooole lot of them will have the same name on them.