Why use polls to find out what is wrong with Sierra adventures? Not only does it give a limited number of responses, of which 0 may fit the opinion of the one answering, but the choices you made really has nothing to do with exactly what someone thinks specifically turned them off to the games.
Anyway... I'm sure you'll get the whys and whynots in the replies.
Me, I loved LSL on PC at school when I was 16. We'd take turns playing and be 4 or so giving the player advice on the only PC with color screen in the back room of the CAD class
But nowadays this type of adventure offers scant reward for the HOOUUUURRRSS of time you put in. When you were a teenager things were different.
SQ seems to be the game with the most variation and fun in puzzles. The major flaw of the series, for me, is that it's just annoyingly slow (and also takes way too long to figure out the puzzles with all that running back and forth with items). Especially if the solution is "give spacebra to poodle".
But they are good examples of easy-to-play (ie. good controls and easy to get the hang of) games, and is time well spent if you have it.
But I prefer a quickie with the joystick nowadays, 15-30 mins max.