I sold my 3DS awhile back to pay for my X68000, which of course was a great investment, but now I'm starting to miss my 3DS. I've been listening to a lot of the mega64 podcast, and on one episode they said selling games at times may be ok (though arguably still bad) but selling your consoles is stupid. You'll probably want it again and then you're just paying for two.
I liked the Mario 3D land a lot and the Zelda LBW game was really great. The game I miss the most though is Animal Crossing. It's so much fun and once I stopped playing everyday, I would feel guilty for coming back after a few days or a week. It was bad, haha.
I'm sort of tempted to get the "new" 3DS for Xenoblade, and of course Animal Crossing. Sometimes I would go through a stretch of time where I wasn't into it, but overall it's a great handheld.