I personally put the "how long does this game get my attention" quotient first on my list when considering a game. Multiplayer games seem to have lasting appeal, and I personally feel more justified shelling out 60 dollars for a game that continues after a story arc is finished. Everyone is giving Journey great ratings, however it is a terribly short game. This is really preventing me from purchasing it, as I feel it will not give me "my monies worth."
Here's a good question: Should one dollar equal one hour of playing time? (60 dollars for 60 hours? If you were to put an amount on each hour spent in a game, would it be a dollar, two, or five?)
Here's the second good question: How do you put a price on a game? (What determines the market value of a game, and who gets to make that decision?)