Having been an afficionado of adventure games over the years, I understand that they aren't without their difficulties. For every Monkey Island or Space Quest, there are four that take the route of Phantasmagoria* and about six different games featuring puzzles with solutions that read like poorly translated stereo instructions. While it's the easiest genre to design for (no combat algorithms or anything like that, clean narrative with a few branches) it's also one of the easiest to screw up. All it takes is one puzzle where processor speed determines difficulty, or pouring whiskey into the gas tank of a car to fuel up a spaceship, or an infuriating pixel hunt and instantly people will throw up their hands and uninstall in annoyance.