Now I take issue with this, despite the point your trying to make.
Games that got 90+ in 2006-2009 can't be changed. But every rational mind would agree that if those games would be reviewed in 2012 they would get lower averages due to changing standards.
Sales aint quality, but it determines level of interest, the act of putting your money where your mouth is. Halo is a gamers game. KZ is more niche since it had significant hype and marketing at the time.