Just keep on exploring. There will be, even if you've completed everything, same as me, you'll always find something entertaining within the world that sparks curiosity and adventure. There are always the easter eggs to find within the game too, little pieces of information that amount to what could be something significant. And there are the people. Sometimes, even if it's not a quest, people will give you tasks to complete. The world of oblivion is literally brimming with stuff to do, even if you're not a role-player. And if that's not enough to get you going in the world again, try inventing a quest by yourself. Set yourself a challenge. Try to collect objects around the game. Weapons, armor, anything. Or try and find something in particular, a person, place or whatever.

I'm sure you'll find something else to find and do in oblivion. And, like you said, if you truly feel like you've expired the game, then start over, play as someone different, be someone different. Instead of answering people with kindness, act harshly instead, or vice-versa. Either way, there is always something for you to find. And if, at the very end, you still feel like you've taken everything oblivion has to give, move on to another RPG. Begin a new life in another world and wait until the epicness of Skyrim storms planet Earth.

Try the Fable series, or even Dragon Age. Or if you're feeling nostalgic, or haven't tried it before, go back in time and play Morrowind again, Oblivion's predecessor. That game was classical in every way, and it is filled with as much life, and adventure as Oblivion had, and more in some regards. So there are always options to sate your exploration and quest finding needs. You just have to look for em. Good Luck ^^

You should try Sacred 2... I spent like 100 hours exploring and killing stuff and I have only seen 5% of the world /cry

Iam actually with you on the "not roleplaying" aspect for the most part. It's not that I have no imagination. In fact, I've written many role plays with my friend, but when playing the game, I really don't care who my character is. I just give them a cool name and go running around doing things.

Have you completed everything in Morrowind? That could be a fun goal.

can i ask you one question? how many quests are there in Oblivion?

Well you can always pick up a quest from http://www.gamesas.com/index.php?/topic/1149955-community-quests/ thread.

I received all 1,250 achievement-points for this game, and would gladly do so again, except that I prefer to stop playing a given title for a couple years at minimum, then come back to it "recharged" and ready to re-experience it from scratch.

Yet, that said, I still manage to find new and interesting things in the game from time to time, and am amazed at how much depth and content the developers managed to pack into it. Replaying this one is a treat.