This is a tough question and the answer is probably unique to each GM and his group of players. I will mention one thing that I think makes a good adventure that I haven't seen above: A plot that is meaningful to the characters on a personal level.
I have run plenty of good adventures where the party goes off to slay some dragon for the treasure or chop up some goblins for the "good of the kingdom". But I find that the best adventures are the ones where the characters have a very personal stake in the outcome of the adventure. Perhaps they are going to rescue a neice or nephew. Maybe they are taking revenge on the goblins who killed one of their brothers. They could be recovering a family heirloom that was stolen by bugbear bandits. Whatever the reason, I try to make the motivation for the adventure more than a quest for more gold, experience points or even for "the greater good".
In my present campaign, the party (a druid, a fighter/ranger and a sorcerer/rogue) is waging war against a group of gnolls that have inhabited the abandoned ruins of a nearby town. The druid wants them gone because they have shown that they have little respect for nature and because he has been promised a large tract of land to put into a "preserve" if the gnolls can be driven away. The gnolls are the favored enemy of the fighter/ranger but he is also hoping to recover some treasure from them that was part of "trust fund" for the families of fallen soldiers, one of whom was his grandfather. The sorcerer/rogue's girlfriend's parents were killed by the gnolls and he is partially pursuing them for revenge. The ruins the gnolls presently inhabit guard the way to some silver mines from which the party has been promised a portion of the profits as reward for earlier heroism. To top it off, the party was earlier nearly killed by the gnolls while traveling on a previous adventure (the one that earned them an interest in the silver mines).
Needless to say, they don't require any prodding to go after the adventure with great tenacity.
So I would say that the party sharing a common goal that they all wish to pursue for important character reasons is one ingredient for making good adventures.