Yes they are trying, you are simply playing port like it was already stated.

If Nintendo wasnt gonna try with the graphics, they would have made the Wii a Gamecube add-on, not a whole new console.

And anyway, you should know by now that the first generation of games on a new console are always slightly disapointing in the gfx side except for a few, the first games out usually didnt had enough time to properly use the dev kit to make a game with OMIGAZ GFX that takes full use of the console...

(look back at super smash bros melee back then, look at Zelda TPP to see the difference betwen early game on a console and late game, or hell, compare SSBM and SSBB to see the gap and realize they do try)