I noticed I've been doing with this a few games/series to friends of mine and it made me wonder how common it is with others. Essentially, the idea is that with pretty much anything, someone will reach a point where they've got a pretty good idea of how a game plays, what they can expect, the tone, the plot, etc and if they reach that point and just aren't enjoying it, there's really no point it continuing on because it's not magically gonna get better. I imagine it might have originally been inspired by Yathzee once talking about how he's quit games at around 90% because he wasn't feeling it and he couldn't imagine that last 10% was somehow gonna change his opinion at this point.
Anyway, off the top of my head.
Dark Souls-If someone reaches the top of the church, rings the first bell and isn't feeling an urge to keep going, there's no shame in quitting.
Assassin's Creed(Series)-If you played 2 and didn't like it, there's probably no reason to play any of the others(except maybe Origins if the RPG thing appeals to you more).
Anyway, off the top of my head.
Dark Souls-If someone reaches the top of the church, rings the first bell and isn't feeling an urge to keep going, there's no shame in quitting.
Assassin's Creed(Series)-If you played 2 and didn't like it, there's probably no reason to play any of the others(except maybe Origins if the RPG thing appeals to you more).