I started GTA IV three times, and I never got to finish it. At the time, when I stopped playing a game and picked it back up after a long time, I was in the habit of restarting. I think that's why I never finished the first two.
As for the third, I actually got pretty close. In fact, I was playing the final mission. But after countless failures, I turned my Xbox 360 off and decided to try again later. However, my 360 broke before I got the chance. And it's still broken.
Yes, it's a rather tragic story, stemming from both my procrastination and bad habits, and the fragility of Xbox 360.