I feel like people using outside assets really don't have that much of an advantage, since free assets usually aren't of the highest quality, and it's really hard to find all the things you need and still have them be cohesive. At least, as far as graphics are concerned. Sound is a different issue altogether. Anyone can make their own art and have it look decent, but making all your own sounds is just not realistic if you want them to be high quality. I think it's a given that a lot of sounds are going to be taken from elsewhere. However, I think the game descriptions/credits should specify whether some/most/all of the assets are their own, so the judges can take that into account.