If you are asking closer to DCA then yeah, GCV is the closest you can get.
But if you are talking both main entrances (DL and DCA) there are other hotels closer, BW Park Place Inn, Tropicana, etc.
See this map below which is a link from DL board.
You can't see the walkway to DL/DCA entrance very well but it's pretty much in front of BW Park Place Inn.
And distances from the compared to GCV, those hotels are closer.
I'll try to find another post about mileages between each hotels to the main entrances if I can find it again.
http://photopost.wdwinfo.com/data/556/11450dlgoodneighbormap1.jpg
Well, after some searching apparently the map was posted on geocities and it was trashed by yahoo.
This is the next best thing.
http://www.anaheimoc.org/pdf/hot_1205.pdf
Again, the pedestrian walkway to the main entrances is in front of Tropicana and BW Park Place Inn area.