Oh lord, I am a mad collector in all senses of the word. Whether it be large or minute, I must have it. There is, as you mentioned, a wondrous feeling in finally achieving this one facet of the game.

In retrospect, however, there is a somewhat bittersweet taste associated with it: the hours upon hours one spends whilst collecting these various artifacts, rarities, and other odds and ends to achieve that great 100% in terms of items; sometimes looking back on these hours upon hours is cause to have one pondering where one's life has gone.

And then I simply do it again on another game, such as Morrowind, where there are literally houses upon houses of rarities and artifacts. Another is Diablo II, where the Elite Uniques and curious high level runes and set items are highly sought after. The fact that there is a certain amount of chance associated with it only adds to its longevity.

Being a person that enjoys playing games until they are weary and weak, I enjoy this mad collecting and side quest running; however, the casual gamer would most likely bash his face through a brick wall if such side quests became a necessity.