Well i think the Wii is the way to go...
Your graphic question, is the Wii has the least in this category but it is not based on graphics it is based on GAME PLAY...basically u are assured a fun time u play not matter wat.
Adult games, Yes the Wii does plan on releasing more games for adults, i myself am looking forward to that. But ill tell u one thing some games i never even thought of buying i have, like MySims, that is a great game and isnt really an "adult game".
nunchuck question, the whole expierance with the Wii makes it feel real not just the nunchuck, everything, it makes u feel like u are really in the game and in control with everything.
Hope this helps