I still play my old DS Lite (I have both a silver and a white one because the grey one's touchscreen was getting unresponsive because of too much Elite Beat Agents).
From time to time I play Picross DS, even though I tend to use the buttons because I'm either too blind to tap the right box or the touchscreen is out of whack.
I still have a years old save of Etrian Odyssey 2 I someday will return to. I bought all three (then existing) Etrian games because I loved the first one.
I should play more DS...