I hate games with endings where instead of having some new features unlocked, and the joy of completing something, the credits roll, and you dropped off where you where before you fought the final boss, and they tell you to go do stuff you've already done before, i mean, i just don't feel like i've accomplished something, and i feel that the game will "never" actually end :(
Examples: LOZ phantom hourglass, M&L Bowser's inside story, professor layton.
It might be diffrent to you, but this is my opinion.