Nintendo really touched on something impressive there, to say the least. For the all the fighting between the trio of consoles, it's a good bit harder to find someone who can honestly say the DS doesn't have something for them. The game library is getting pretty huge, the design is sturdy (I have both designs, the original and a Lite, though no DSi), and companies keep getting more innovative with the controls.
Not to mention it's become one of the most massive RPG systems I've ever seen. I never thought I'd see this many but I think I've attained Geek-vana here with the sheer numbers. I think that's my thing, really: fairly good graphics with a focus on story as well. The DS RPGs seem to handle that pretty well.
All in all, I hope the DS keeps on trucking. The fifth year North American anniversary for it comes up in around a month.