Have you (or your significant other) ever been sitting on the couch, mindlessly watching an edited-for-network-TV movie, replete with commercials, even though you own the same, unedited, high-definition, 5.1 audio movie in your DVD collection? You may even offer to drop said DVD into the strategically placed player, mere inches below above TV, only to be stopped short because "they're just watching it because its on." Because it would be silly to watch it if it wasn't on.
It the very same enigma that means the living room PC will never take off, as so observed by Slate. A media center PC would mean finding the remote, switching to the right input on the set, navigating through a few menus, deciding on an option, then actually hitting play. The alternative is randomly navigating channels until you find a Full House rerun. Whilst you may have a more edifying experience with the former, the cerebellum would rather turn itself completely off and opt for the latter.
It's also the same reason why Internet Explorer owns the majority share of all browser traffic, in spite of its awesome list of well-observed glitches. It's why so many people play solitare on their PC. Hell, it's why Windows won the OS war. It's just on. It's already there, and installing/inserting something different would require the cerebellum to turn back on, and unfortunately 50 hours of mind-numbing tomfoolery at the office has beaten it unconscious.
If one wants to penetrate the vast sea of casual gamers out there, you have to make something easier to aquire than finding a DVD and watching it on the TV. Why are Flash games so popular? Bingo. Easier than a DVD.
Mebbe the next frontier isn't the game per se... it's the installer. Direct into your brain. Or whichever pieces of it remain working.