For those of you who are interested in modding Oblivion, here are some guides from Something Awful forums where they walk you through managing many addons and suggest the best ones:
They also have a great thread on modding Morrowind, and with some of the mods they've suggested, I would highly recommend replaying Morrowind with these mods, especially if you've never completed the main storyline.
As for new games, I was in the market myself and greatly appreciate the contributions in this thread, some of the trailers for these games look like a lot of fun.
The SA posts above are actually quite a good resource. It will definitely seem like a lot of work to get that many mods working correctly, but it's worth it for just how utterly amazing the gameplay ends up being when you do.
As for Morrowind vs Oblivion, I too prefer Morrowind for various reasons (and have probably spent 10x more hours playing it), but Oblivion is fun in it's own way and I focused on it simply because the OP seemed concerned largely with graphics.