PopCap Games said its U.S. retail revenues for PC games were up 85 percent in 2008. The Seattle-based maker of casual games managed to pull that off in a year when U.S. PC retail game market fell 14 percent to $701.4 million (see below).

The private company doesn’t release sales figures. The results were reported by market research NPD. The biggest part of the growth happened in the fourth quarter thanks to the launch of Bejeweled Twist, the latest game in PopCap’s huge Bejeweled franchise. PopCap’s games are now sold in 20,000 North American stores.

Bejewled Twist ranked at No. 8 on the list of best-selling PC titles during the peak December month. Other top sellers included Bejeweled 2, Zuma, Amazing Adventures The Lost Tomb and Mystery P.I. — The Lottery Ticket. PopCap now has 15 titles available for purchase, up from 10 in 2007. And Bejeweled alone has sold more than 25 million copies across all game platforms.

PopCap’s growth shows that there is still a lot of demand for casual games, or those that are akin to game snacks with fun basic mechanics. It will be interesting to see revenue numbers for the entire industry in 2008, since casual was one of the hot investment sectors of last year.

PC retail sales have been heading south for a while. The last couple of years, NPD and the Entertainment Software Association have been burying this news in a press release about software sales for the entire year. I’m not sure why they don’t break out more information on the PC retail games market, but it’s clear they don’t want people to focus on the decline in sales, which happened despite big launches like the World of Warcraft Wrath of the Lich King launch in the fall.

The natural comeback for the PC advocates is that PC game sales have never been stronger. They just aren’t reflected in the numbers because much of the revenue is generated via ads for free games, virtual goods sales, or subscriptions to online games. In that scheme of things, PC gaming is growing.