Oblivion is a great game. No need for mods, in my opinion, the game is exceptional as is. Progress: I finished the Dark Brotherhood questline, have done a few quests in various other guilds, have done quite a few random quests that people give you in towns and whatnot, and have done.. probably at least half of the main questline. Total hours so far: around 30.
I've played a small bit of Morrowind, and although it was likely among the best PC RPG's around at the time of its release, it doesn't compare to Oblivion (as expected). There is little voice-acting and vast amounts of reading, which help turn the game into more of a chore, and the easy checkpoint/map navigation in Oblivion wasn't written at the time. Combat in Morrowind isn't as grand, either.