Which guild in Oblivion has the best quests?

I really liked the Thieves Guild a lot as well. The Ultimate Heist quest was particularly long and interesting, plust the loot involved was really nice! I never knew there were that many dungeons under the IC till then. The DB is a close second with quests like Whodunnit? as well.

My favorite guild is the mage guild.
i always start by it, at least to have access to spell and enchantment creation.
i like the thief guild too, and also the dark brotherhood, but i find the fighter guild quests boring.

I didn't vote because I think it was only the mages guild I finished completely. I loved the Dark Brotherhood simply because of Lucien BUT knowing what would happen to him if I kept playing it, I stopped because I never wanted to see him that way but I would have to say the Dark Brotherhood even though I never finished it. I just fell in love with his character and could not continue with the quests. On a side note, I knew his voice actor. We corresponded a lot and he even told me once when he was going to be on TV show as an actor, not a voice actor, he's a really nice guy. He was also Mr. Burke in Fallout, yet another reason I fell in love with Burke--I love those bad boys.

Here's a really awesome video made by a friend of mine about the Dark Brotherhood. Mmmmmmmmmmmmmmmm Lucien!

http://www.youtube.com/watch?v=R8ldEB5DOaU

I did finish the Theives Guild also, come to think of it. I used Slof's drow race for that guild. I did like the Theives Guild in all the games I play if there is a stealth/theif choice, I usually go for it. Unless I was playing Slof's Xivilai's then I just blasted in, killed everyone, raped them and got on with the quests. Here's the Ulitmate Heist from my friend, this is another awesome video!

http://www.youtube.com/watch?v=fV7hfS0vFCQ

ShadowFox wrote:Dark Brotherhood by far.
It is so awesome, if only more were like it.

I agree. Many other guilds have quests that don't seem to affect the outside world at all, whereas the Dark Brotherhood offers major back stories to all quests. Also, many of the quests offer at least 2 way to complete them; this gives the players many more options.