Your not going to be able to change it. Any type of rating system turns into a popularity thing. The star system you mentioned would be no different, in fact it would be easier to get top charting. Just click a star on every image and leave. Most of what I have seen going on in the gallery is not how good the art is. It's how many you know and comment on or what group you join.

Take the rating system totally out and you would solve the whole issue. Comment all you want on an image, it does not mater because they are not being counted and no charts made with those numbers. The drawback of that would be, you would have to actually look at images that are not part of the popualrs or groups. How else would you know if you like them, they aren't racked in the top 20 or have the most stars.