I'm looking forward to the E3 show, because most likely, IGN will host alot more videos and lovely screenies of in game action
As for the Wii, it should be good yes, and, while some question the power, take this into account.
The Xbox 360 is a HD device, and always outputs at a HD resoloution, and so does the PS3.
Now, the Wii doesn't, so alot of its graphics capability doesn't have to be forced to run this high, so can run at a standard TV (with interlacing, if supported) and so, the graphics don't have to be pushed as hard, resulting in possibly, sometimes, the same graphics power in games.
Thats not to say it'll run the Unreal 3 engine (No idea, but it doesn't really ring true in my eyes, unless I see it of course
), etc, because I believe it won't, but in terms of image quality, I believe it should be right up there.