But that would require a judging system on what maps are high quality. Some maps are even 'fun' maps and therefore sacrifice quality but they might be extremely popular.
You are right, and there is a well known example which is the Paint series, no 3d textures, no lighting (i.e. low graphics quality), but is fun to play and I find many people playing it, and the evidence of its success that it keeps giving sequels (we now have 9 Paint maps).
so I suggest other system:
Why not we make a rating system according to the following:
1 - Architecture
2 - Texturing
3 - Lighting
4 - Other eye candy (like additional models) (if available)
5 - Overall graphics
6 - Gameplay
7 - Overall rating
Then the user will select what he wants, the one who likes good graphics may pick what he wants, and the one who wants good gameplay whatever the graphics was will find his map, etc...
But I think this will not prevent making a section for the beginners (like me) to post their trials and recieve constructive comments so that they could learn and improve their skills until they make good maps, so he could join this board.