If your friend's a fan of RPGs, it's looking like a great move. Aside from the DS library, we've already seen Etrian Odyssey IV and Fire Emblem Awakening this year (and I guess Pokemon Mystery Dungeon, but it's terrible both as a Pokemon game and a roguelike), Devil Summoner: Soul Hackers is out in a couple weeks, and Shin Megami Tensei IV is out in July. There's also Luigi's Mansion 2 and the new Animal Crossing game if he enjoyed the Gamecube games. And that's to say nothing about the games from last year and the year before.
I don't know if trading the PS3 straight-up for an XL was a good move, though; you can usually get them for $120-$140 in good to great condition on Cowboom, but they're rarely in stock very long.
Horrible move. The only games worth owning on 3DS IMO are Fire Emblem: Awakening, Castlevania: Mirror of Fate. I have about 6 3DS games but it's garbage compared to the PS3. Though I will say while playing my 3DS games I stuck to them but once I beat them I went back to PS3. My Fire Emblem 3DS is probably worth more than a PS3 at this point <_<
Why don't you go take a jog? Better yet, go kick some rocks. Let me guess you have a blog, follow trends like it's your job.