If we had a system whereby the top 10% rated maps automatically made it into the official rotation that would mean I would vote more. I.E. the better maps get rated and therefore are available.
There are 3 or 4 fantastic maps that are now gone forever - I can't even tell you the ID as they have dropped off my profile.
I think the main problem is that there are not enough players for the current rating system to make any sense.
I also agree with ditching the description text and making it 5 stars for two categories - Fun and Map design.

You could always just only reward exp points for voting to people that either have completed the map, or completed at least a percentage of it. That way everyone can vote, but only those who have thoroughly tried the maps will earn exp off it

If there was an Achievement for rating 5, 10, 20, 50 maps, people would do it.