It depends on the game in question.
For example, my current three most played games are World of Warcraft, of which I've played since the very start. Football Manager, of which I play daily, for a couple of hours, until the new one comes out.
Currently the Sims 3, which will take up a fair amount of time.
Team Fortress two, and Left 4 Dead, took up a lot of my time.
Half life, and Half life two, were almost the perfect length for the type of game.
Call of Duty: Modern Warfare was very short, but was packed to the brim with brilliant action.
Games can all have different lengths, It's not the length that bothers me, its the content.