2013 by a mile

Lineup wise 2013 is better. Animal Crossing, Luigi's Mansion, Fire Emblem, new Zelda, new Pokemon X/Y, Monster Hunter 3G for the US, Monster Hunter 4 for Japan, etc.

2013 easily wins in my opinion! In 2013, the 3DS had Luigi's Mansion, Zelda, Pokemon, Fire Emblem and others!

2013 is probably the highest the 3ds will ever go! It was basically like having an orgasm of excellent quality games one after the other! Nothing can ever out do that, for better or for worse. But 2014 is still gonna be a fun year!

Well, Smash Bros is fun and I am gonna play it till I get sick of it (which is never) but it cannot replace the amount of awesome games we got last year... Smash Bros is basically equalvent to Pokemon with less sales imo

2013 easily. Though this year won't be toooo bad.

Sale's wise 2014 is... Well 2013 will still be better. But hey! Omega Ruby and Alpha Sapphire!

Are we talking sales-wise or personal preference?

If personal preference, 2014. Pokemon OR and AS have already made this year a better one.

Fire Emblem, Animal Crossing, Pokemon X/Y, and Zelda are an unbeatable combo for me. One of the greatest years in my gaming life, not just the 3DS. 2014 will do fine for itself though, but the only major titles it has is Smash and Pokemon OR/AS right now. For me that is. Kirby, Bravely Default, Chibi Robo, and Tomodachi are minor but still important titles for me, but they're countered in 2013 by Luigi's Mansion, Shin Megami Tensei IV, Mario and Luigi, and Etrian Odyssey. There are other very good titles in both years that balance each other out, but overall, Smash isn't enough to stand up to last year.

Now all of that is just from a personal perspective. If I were to try to give an unbiased, more objective guess at the potential of each year, from what we know so far, I'd still say 2013 wins. A Pokemon remake doesn't stand up to a new gen, sorry. Smash is big, but Smash and a Pokemon remake together are only about enough to make up for the new gen of X/Y. Stack Fire Emblem, Luigi's Mansion, Mario and Luigi, SMT IV, and Animal Crossing against Kirby, Bravely Default, a subpar Yoshi game, a new life sim, and a few other washed up IPs, and 2013 comes out on top. That said, I have a feeling that E3 will make up for some of what 2014 lacks thus far, and justify Nintendo's 13.5 million projection for 3DS hardware this year. I'm not worried at all. 2013 was a gaming high I might never reach again, at least with portable gaming, but 2014 should be enough to prevent me from crashing too hard off that high.

Nintendo's projecting 12 million 3DS this year, something they'll probably miss at that.