While I think the Wii can make some lovely GFX in it's own right, a couple of points:
* Those oblivion shots are very suspect. The game looks downright stunning in 'reality' and quite a bit better than what those shots look like. Seems like someone took part of the screen and blew it up or something. (True, it has some less stellar bits, but the pretty parts are *very* pretty)
* I'm not overly impressed by the Zelda / Metroid / Super Mario shots even so. Yes, there's nice GFX on them but they're obviously lower res.
This is not to say they don't look nice, it's just that the other next-gen consoles GFX looks -quite clearly in almost all cases and that does include Oblivion- much nicer than even that.
But it's ok really. The Wii has graphics that are good enough. It's draw to me never was GFX to begin with and I suspect that goes for most Wii owners. Lack of pretty GFX don't stop me from loving Wario Ware Smooth Moves, Wii Sports, etc.
Edit:
I figured out whats 'wrong' about the Xbox 360 shots. Somehow my browser only shows the left part of them so it looks really odd, I miss about 30-40% of the pictures (they are there completely but I had to manually click 'show image' to see them).
Anyway, looking at these screens properly (i.e. full screen for a picture not as inline) you can clearly see the Xbox 360 shots look quite a bit better than the Wii ones. Don't forget that what these screenshots show is in fact what you'll see as a full screen on your TV when playing.










