The handheld market is pretty damn big right now.
I'd get a 3DS for Mario and Luigi: Dream Team alone. The M&L RPG games are easily 24 hours of content minimum and are worth more than two playthroughs. People I know loved Luigi's Mansion: Dark Moon and Fire Emblem: Awakening. Fox already mentioned Animal Crossing but I was never really a fan of those games myself. I can't keep track of all the new pokeymans, but X and Y honestly look to be the biggest steps forward since Gold and Silver (or HeartGold&SoulSilver).
I also like the Vita, but that's got a lot more JRPGs than the usual consumer would like
EDIT:
I would recommend the regular 3DS over the XL purely because of the size unless you're honestly looking for a handheld that feels like a tablet. One of the older kids at the camp I work at has a XL, and I took out my Samsung YP-G70 to compare the size. The YP-G70 is a big-ass minitablet media player, and the XL was easily two of them when open.