Lots of interesting opinions on this topic. I would argue that the golden age would be from about 2002 to 2005. During that period, RV sales were beginning to boom, many new competitors arrived, and all the manufacturers had money and motivation to build better coaches. Huge basement storage, massive front windows, and multiple slides became standard.
From 2005 to 2007, they were all just pushing them out as fast as they could for the endless money that people accessing from the housing boom.
From 2008 to 2010, free money ran out and environmental regulations made things more difficult for chassis manufacturers. Not a happy time for anyone in the industry.
So, for my vote (if there was a vote), I would pick 2002 to 2005.