It's not going to be a huge leap in graphics
Say from Daggerfall to Oblivion.
It's going to be more like from Morrowind to Oblivion, in other words it's going to look better and feel better but it's not going to be a huge leap in terms of graphics like people are thinking.
That's a terrible anology. Daggerfall is a pseduo 3D engine similar to Doom. Morrowind is a true 3D direct3d 8 engine made nearly a decade later and Oblivion is a direct3d 9 engine an entire generation ahead.
Skyrim is most likely a direct3d 9 engine and based upon what we know it's most likely an enhanced fallout 3 engine (not truly a new engine). It's intended for the exact same console generation as Oblivion and the screenshots are not at all leaps and bounds better than Oblivion. When comparing a late generation console game to its early generation there is always going to be a noticeable difference in visual quality, but never ever ever has say a late NES game looked like a early SNES game or a late PS1 game looked like an early PS2 game, etc. The longer a console generation pans out developers will always learn better tips and tricks and squeeze out better visuals but you can't squeeze out that much.
Also keep in mind that microsoft once had a rule that all games had to be 720p, something they lifted so devs could make somewhat better looking games at a lower resolution framebuffer. Red dead redemption might look really good at times, especially in screenshots or from a distance, but the framerate is 25fps average which is less than what used to be considered the minimum playable framerate (30fps) and often it goes into the teens. Plus the PS3 version (and maybe the 360 version) has a 640p framebuffer.