WiiWare/VC Transfer - Free or a couple bucks
HD resolution
Graphics that are at least on par with 360 and PS3
An ethernet port so people can have faster downloads
Hard Drive and/or at least have people use USB Flash memory and SD cards
In and Out of game enhanced friends features and voice chat
An achievement system of some sort that could actually make them worth getting (easy ones don't really matter - harder ones give you more bragging rights or something)
Backwards compatibility with Wii games (upscaled and sharper) and accessories
Better channels that allow more interaction and competition with friends and also linking to social networking sites
The ability to create your own channels
Better rewards program for buying Nintendo Products and add something for digital items as well
More innovative exclusives