I have a confession to make: I never finished Shadow of the Colossus.
[Take a few moments to catch your breath, bring your blood pressure back down to normal, and snag some smelling salts to revive any of those nearby with delicate constitutions.]
In fact, I never made it past the fifth Colossus. It wasn't because the game was bad or horribly broken in some way. I had my issues with it, but if I'm honest with myself the reason I chucked it to the back of the game drawer was because I saw what was coming, and I didn't want to have any part in it. It was clear from the beginning that Wander was planning Bad Things, and that the voice instructing him was a Bad Person, and the thought of pushing through two more handfuls of giant hairy beasts only to accomplish something with which I didn't agree simply wasn't going to happen.
So why is it, then, that I so gleefully danced through Xseed's Pandora's Tower?
It is a (very) minor spoiler to mention this, but since 95% of you will likely never play Pandora's Tower, I don't feel too bad. As the game progresses, you feel a similar sense of foreboding that your actions in the game are leading to some very disturbing if not outright terrible outcomes. In many ways the game presents the same sense of stride-halting dread that Shadow of the Colossus does once you piece together a few facts. With both games you (as always) have the choice to continue playing or foist the disk off on some unsuspecting passer-by. Although there are some interesting mechanical tricks that Pandora's Tower employed to string me along, if I had to pinpoint one reason it had me so engrossed while Shadow of the Colossus had me so repulsed, it would be this: empathy.