Most of these Gold CDs are transferred with greater attention to detail, and using better mastering engineers than a lot of the run of the mill major label CDs that you see. (especially with the early edition CDs that often got transferred with no involvement from the original recording engineer/producer or artist, and without accounting for whether the original master tape was tweaked to sound optimal on vinyl) With a lot of the poorly done CDs, just some better mastering would improve things greatly, regardless of whether the material is gold or aluminum.

Does the gold layer affect the sound quality? The only way you can answer this question would be to have aluminum and gold CDs pressed from the same master source. And none of us have the studio access required to conduct such a test. So, you're left with comparing the actual discs, and if the gold CDs do sound better, then the substrate material is but one of many variables that potentially contribute to the higher sound quality.