Oblivion, yes. Figure high settings around a 1280x1024 resolution...or 1440x900 if widescreen.
Skyrim is anyone's guess. Requirements aren't even out for it yet. It'll probably run, but couldn't say for sure how well. My educated guess would probably be low settings, maybe medium.
Not quite.... These are just an estimate, but they should give a decent benchmark of what to expect.
Skyrim minimums:
CPU: Core 2 Duo/Athlon X2 or better
RAM: 1.5 gig
Video Card: NVidia 7800 Series, ATI Radeon 1800 Series or better
VRAM 512 MB Graphics memory
Storage: 12 gig
Sound Card: DirectX 9.0c Compatable
ODD: DVD-ROM
DirectX: DX9.0c