So when I picked up Bioshock about a year ago, it was as part of a double pack with Oblivion - which I'd never heard of except in reference to Fallout 3, and which the packaging seemed to warn me off from playing on Vista. Of course, I actually got it running really easily, while Bioshock required all sorts of hoop-jumping, and ultimately crapped out completely on a later level (and when my video card is working fine with everything except Bioshock, I think I'll just leave it be, thanks). A year later, I'm still playing Oblivion every so often.
I guess "medievil Fallout 3" is an accurate description, although I enjoy it in a slightly different way. For a start, where I've also enjoyed Fallout 3 as an exercise in character creation and (slightly painful) NPC interaction, I'm playing Oblivion as pretty much a straight explore-em-up. My best discovery yet is that I can play as a mage who can constantly cast invisibility spells when that beauty spot I stumble upon happens to also be home to a minotaur. And that also opens up a lucrative market in robbing and murdering the braindead NPCs that infest the otherwise picturesque landscape.
In fact, playing a criminal seems to be the strongest way to play the game. Not only do I get intimately acquainted with otherwise minor characters as I rummage through their belongings, but I have an incentive to learn their daily schedules and avoid them as they go about spouting repetitive inanities. Still, I think the fact that Oblivion is trying to simulate a relatively stable world actually makes it a little more consistently believable than the much sparser but no less stable post-apocalyptia of Fallout 3. And, more than its better known successor, where I think Oblivion succeeds is in creating a world where, even if you find the more obvious forms of gameplay not to your liking, you can still make a compelling virtual living as an invisible burgling rambler.