great point! would be interesting to see the average sales drop-off over time. Typically games have sales spikes during the early release and then later during

great point! would be interesting to see the average sales drop-off over time. Typically games have sales spikes during the early release and then later during sales, but it tends to drop off over time. "Classic" or "must play" games, however, like Portal, tend to sell pretty well over their entire life.