POSSIBLE SPOILER
I always end up creating a character, rising through the factions and houses that fit into the profile of whoever I'm playing, and become top dog in anything I do. Meanwhile, I'll go along with the main quest, usually picking up the random dude's skull in his tomb south of pelagiad right away so as to avoid the bug where Sharn maz-grurluduburdubidum in the balmora mage's guild disappears... (It's a b****)
Eventually I'll become the Nerevarine, and then I'll realize that I'm not actually the right guy for the job, and start over again with a new and exciting character!
Like dragon wench said, the lust for something different wins through, and I start again. I have -never- bothered to finish the game, even though at one point I had gotten all the artifacts and was ready for the final showdown with Dagor Ur. I just left my super-warrior in red mountain & started over...
I think with my two latest characters (an unarmored high elf monk & a wood elf ranger) I've pretty much been there, done that... At least for the first 20 levels...