Peter points to games that have a social networking aspect as the place where the Mac shines. These games, at least the ones he mentions, are online games which can be played on either Mac or PCs so lumping these in as 'Mac games' seems a little disingenuous to me (though they can be played on a Mac).
Peter expounds on the benefits of computer gaming as compared to console gaming, but I think he falls short of crafting an argument for the Mac as a gaming platform.
Are there many Mac gamers out there? None of my Macs have any games installed on them, but perhaps I am in the minority.