Dragon Age: Origins, Awakening and Witch Hunt, Because they felt satisfying to complete.
When you save the world and you find out what happened to all your friends, it was bitter-sweet for me, especially when some of them went on to have a painful future, and the music during those scenes and the credits brought a tear to my eye. But witch hunt was my favourate out of them, as
[spoiler/] I went through the portal mirror thing (can't exactly remember it's name) with morrigan, and it just cuts out.[/spoiler] Now you could say that's rubbish, and you feel cheated of a ending. But the fact that there was no explanation at the end shows you that this is were your tale finnally ends, it's over, your burdens are lifted, and you know that, what ever happens, you do not have to worry anymore, your safe.
That's why I like it.
Also, Fable II's ending really got to me. Mostly what I said above, it's bitter-sweet, burdens have been lifted, you'll never see your friends again, but it's all been wrapped up.
And Portal 2 for exactly the same reasons.
It's not like I didn't like playing them, but You finish the adventure, and now it's time for another one, a new one. A game that wraps everything up in a neat bundel is satisfying and you can continue your games safe in the knowledge that everything is alright with that game world.