The primary category by which I judge [by which I mean in the neutral sense of "form an opinion on"] cosplay on is how well it is constructed and presented. A well-made, well-fitting costume with accurate or creative accessories and styling (wig/hairdo, makeup, etc) is almost certainly going to look better than a something pulled together from cheap fabric remnants and thrift store pieces. Good costumes are good costumes, regardless of the build of the fan wearing them.