I played Oblivion first couple of times through with a rig with 1GB of RAM, a 6600GT and a mid range single core CPU.
It was still great fun, but when I upgraded my PC in 2008 I went back to it, and it was like a whole new game. Going from minimum settings (5 yard view distance, 60 second loading screens) to fluid playing at maximum (I can see that wolf that's about a mile off and a few pixels on my screen) is just epic.
I don't expect my current rig to handle Skyrim in it's full glory, but I'd like not to be playing on mimimum. Hope you're listening Bethseda