Replayability (amongst Video Games)

Do people really value this as much as they think they do?

Post age 18, I can only think of ten or so major releases (not arcade-esque titles) I've played through more than once, and about three (Half-Life 2, KOTOR, and Gears of War) I've played through more than twice. Half-Life 2 currently holds a rather unique status: it is the only video game I've played more than once on the same difficultly level (in my adult years). On the rare occasions I replay games it's uniformly to test out a different setting or game mode. I.e., Guitar Hero.

I was kind of startled to realize just how little replaying a game mattered to me. Multiplayer isn't even as important as I would have thought, considering that I've only used it extensively with two or three titles (Halo 3, Rainbow Six: Vegas, and Crimson Skies come to mind) over the last five years.

This topic came to my attention primarily because it's the "big knock" against Bioshock. No multiplayer, most of the "shock" value wears off on a second go-round. But then again, do folks really value replayability?