First i want to say something about the capabilities of the Wii. Almost nothing is known about the graphic chip 'Hollywood' used by the wii. Even the clockrate of 243mhz is not confirmed by Nintendo, so you simply cant say what the wii can and what cant do graphic wise, even after 1.5 years.

For determining the grapic power of A6/A7 you must also consider that the engine can be enhanced with plugins. If you don't use this feature it is a lot of work to achieve Next-gen effects or even impossible. If you do you can achieve exactly (at least more or less) the same quality as those AAA-games, it is just much work (sure somebody will say "hey if you do that you could also write your own engine", well maybe, but there are some feature of A6/A7 like memory managment, simple scriping language, editors, level format, collision detection etc etc which saves you a lot of time).

I read often that you must use tricks and hacks to do this and that, i don't think that these are tricks this is just how you program 3D-games. Everything is about faking, this begins with basic techniques like LOD or even normalmapping and ends with scene managment, streaming techniques and so on.
If you want to program a top-notch game you must know every point. A6/A7 only gives you some basics, which doesnt mean that you have to program plugins, most of the things you could even do with c-script (like programing portal reagions for scene managment).

All in all 3dgs is what it is supposed to be, a system for hobbyist with the abillity to extend it.