I'd lean towards quality, the Portal thing is a great example of being a few hours gaming that's wonderful, when so many games pretty much drag out a few hours gaming over 20-40 hours to give the illusion of value for money.
Having said that I can totally go with the food analogy too, especially when you look at classy restaurants, sure, a $20 steak dinner is generally twice as enjoyable as $10 spent at McD's, however, blowing $500 on a gourmet meal isn't going to be 25 times better than the steak, hell, it's probably not even twice as good again, that sliding scale really drops off at a certain point.
I guess that's why I play WOW, I'm not jumping on the bandwagon of knocking it, but for my monthly fee, I get a lotta entertainment, not triple A, but good enjoyment, with decent people, or I could buy a new game every 4 months and HOPE it's good enough to amuse me for the next 4 months.
Of course, sometimes you can treat yourself to a luxury like Portal where you get huge pleasure for just a couple of hours.
