I don't particularly need a different experience from my portable system than from my home console. It does need to be a little faster-paced and easy to save and quit, but otherwise, why would I want a different experience?
Well, the answer is that I'm into videogames and I'm into seeing what new concepts game developers can come up with on the DS. But if someone else out there is perfectly happy with games the way they are, then a "watered down" version of a home console game that they can take with them is perfect. Even I see the appeal: I play games more on the bus than at home nowdays, so I'd be happy with a portable system that plays pretty much the same kind of games as my GameCube, as long as it does it well.