I was having a discussion with a friend of mine, and I was wondering if the "game length" is really the stand alone best metric for the value of a game. Portal is one of my favourite games of all time, and it's short. But it was also cheap. Would I have still bought it if it was $60. Hard to say.
At the same time, I have played games that were very long, that were less interesting. Games like Morrowind and Oblivion. I also found the core game of Mass Effect quite entertaining, but all the extra content filler being a sore spot of the game.