Bastion, and is that a damn fine game, downloadable or otherwise. That man making love to your ear with perfect timing to the beautiful, hand-drawn events...*ahem* excuse me.
I have this weird thing where if I feel like a game might be ending soon, I reflexively quit because I don't want it to stop, even though all I'm doing is making it stop. For this reason, the last one I beat was FFXIII (13), and I hated it, bitching about everything that was wrong the whole time. I guess I didn't care if it ended, but now that I'm thinking about it I gotta get that problem fixed. If replays don't count, then it was Dark Souls PC after some extensive modification, after beating it 3 times on PS3. Yeah, I'm as confused as you might be.
Also, I've played MGS 1-4, but only beat the first 2, and the second is my favorite one. Yep, getting a catscan, don't worry.