The New York Times has taken a look at the NPD's list of top ten selling games in 2007, which shows mass-market games mixed in with games designed for the "young-male audience." As the industry matures and becomes more popular, the "hard-core gamers" and "old-school critics" are becoming just one small part of a very large $18 billion pie.
The NY Times makes its case by observing the absence of critically hailed single-player experiences (like BioShock or Mass Effect) from the top ten, now filled with accessible multiplayer games like Halo 3 and Call of Duty 4. In fact, nine out of the top ten games actually have a multiplayer component (Assassin's Creed is the black sheep). The NYT concludes that people want "human contact in their entertainment" and gaming's mass acceptance comes from being able to have others join in the fun.
A reasonable conclusion, albeit one that oversimplifies matters. While the social elements of most of these games certainly form part of the appeal, the top-selling games also offered compelling solo components. Why choose between single and social gaming when you can have both?