I think "It's Nintendo" best sums it up. I mean, obviously games are a major part, but when you realize, it's a Nintendo system, then that always means you're more than likely to see games like Zelda and Mario and other Nintendo franchises.
The touch screen and having two screens though is really awesome. At E3 2004 when I played it for the first time, I was really impressed by that particular interface. It felt like it was bringing something new to the table, and this year's E3, with games like Trauma Center and Trace Memory, only reinforced that idea. And Nintendogs!