Gamasutra - Staying Power: Rethinking Feedback to Keep Players in the Game

An excellent article with some stats about completion rates of some AAA-games. COD4: close to 80%; GTA4: less than 30%. GTA4 sold more copies and was much longer, but does that account for the difference, and is it worth developing all that content if nearly three quarters of the people who buy the game won’t see all of it?