Well anyway, it would be really neat, I like this idea.
Just wait until you play Oasis and see some of the ingenius quests I have cooked up.
For one, most of them tie in with the story, if they don't then they have their own story. (like mini quests) Plus there will be difficult and elaborate quests, and even quests for things you wouldn't normally quest for (on graal)
I think cool quests are the kind that trueheat described, as well as saving villages from evil or something, quests that tie in with other quests or a huge quest, quests you must complete in order to access new areas, quests that don't REQUIRE more than one person but would be better done in groups. (such as defeating a big monster)
I don't know about the whole one item in the game thing, but perhaps you beat the incredibly hard monster or something, and there is a treasure room with lots of treasure but you can only pick one object, and you have no idea what it does until you have left the quest and perhaps taken it to some wise person to explain the item.