little details, items, eat/drink/sleep, quests.
Have you played Oblivion already? yep
What sort of things interest you? Immersion, roleplay
What type of Character do you usually play? (good/evil, theif/mage, roleplayer/random-no-story-hack-and-slasher?) All of the above
When did you leave? Quit playing when Fallout New vegas came out (Console oblivion) and quit playing PC oblivion last spring when my PC died
What did you not like about Oblivion? What did Oblivion not have or need more of? Loved it, just wanted more of it
Male or female character? I play both, but I don't like the nudy mods. Actually using Hgec underwear version and am thinking of DLing roberts male.
Let's see....
For items you can check out this topic:
http://www.gamesas.com/index.php?/topic/1167983-integrated-items/
I don't use any of those mods but I've heard a lot of a good things about COBL, RealSwords, and Armamentarium.... the seem pretty lore abiding and Immersive.
Little details: http://www.tesnexus.com/downloads/file.php?id=19847, http://www.tesnexus.com/downloads/file.php?id=27029, etc. The earlier suggestion of checking the top 25 is good, but seeing as how there's only 113 mods in the category you might as well just http://www.tesnexus.com/downloads/cat.php?id=78. http://www.gamesas.com/?showtopic=1053088&hl=
Eat/sleep/drink... Sadly I can't really help you there, I've never really paid much attention to those type of mods, don't know why... Maybehttp://www.gamesas.com/index.php?showtopic=1092398 will help you find some.
Quests:In one of my copy/paste links I listed a lot of quest mods and described their immersiveness, execution (ie: do you get quest updates out of the blue, or something more immersive), and story/lore. Here's the http://www.gamefaqs.com/boards/924363-the-elder-scrolls-iv-oblivion/51137901. If I had to give you a list it'd probably be the ones already on that list of my "must have" quest mods. Dark Brotherhood Renewed is a fairly new quest mod which as I recall was pretty immersive.
Mostly I just have to massively recommend 'Integration: The Stranded Light' like I almost always do. Lot's of choices/consequences, multiple solutions, tons of character development, filler dialogue, tons of lore, and just a lot of ways to roleplay, and explore many possibilities.
For roleplay maybe check out http://www.gamesas.com/?showtopic=931523&hl