Well, we know that Nintendo's Wii will not feature true 1080p high definition games as the Xbox 360, but we do know it will support 480p and 16:9 widescreen. Honestly, graphics don't matter much at all in the end the make the game, but if you have the option to have the graphics, why not get them. Keep in mind, that the system has the potential to support true high-definition, but from the way it's layed out right now, it's pretty unlikely to happen (if we can hack a way to do it, I'll let you know as soon as it happens!).
But anyhow, to get the 480p and the 16:9 widescreen graphic options, you will need your handy-dandy compnent cables. So, if you already got your component cables for Gamecube... it sucks to to be you because these cables were designed specifically for the Wii.
Once again, you can only by these special cables from online retailers, like Target.com and so forth, but your best bet is http://store.nintendo.com Lukily for you guys, these cables will be availible at launch for $30. But guys, if you do not currently own or plan to purchase a high-definition television set, than don't buy these cables because they will not work for you.
Keep in mind that in my review of the Wii games, I will be using these component cables. So, if I start raving about the graphics and you don't have the cables then what you see in that game, is the best you'll ever see without them. Just keep that in mind...
One more thing to keep in mind is that 95% of Wii games will be progrssive scan compatible, thus their graphics will be improved by using the cables. 30 of the launch titles will be compatible with progrssive scan, as of now.