I've had my 3DS since the XL launched in the US last August and have accrued a collection of 13 titles since that time, most of which were purchased this past fall/winter with the crazy Christmas sales.
However, other than perhaps Resident Evil Revelations and Shin Megami Tensei: Devil Survivor: Overclocked, I feel that the greatest and must-have titles for the system only came out in the past couple of months. Fire Emblem:Awakening, Etrian Odyssey IV, and Luigi's Mansion 2: Dark Moon are all absolutely fantastic, GREAT values (play hours per dollar spent), and 100% new experiences (read: not ports). That isn't to say that Zelda, Mario Kart, the Mario titles, Final Fantasy: Theatrhythm (and others) are bad by any means, but I cannot say that they provided the same impact as the three aforementioned recent releases.
With upcoming releases like Shin Megami Tensei: Soul Hackers, Shin Megami Tensei IV, Mario & Luigi 4 (and others) in the next couple of months, an RPG enthusiast is going to feel right at home on the system.
Of course, this is an opinion-driven question (and I have, as such, provided an opinionated response), so take these words with a grain of salt.
- Super Mario 3D Land - Luigi's Mansion Dark Moon - Kingdom Hearts 3D - Tales of the Abyss - Resident Evil Revelations - Code of Princess - Fire Emblem Awakening - Kid Icarus Uprising - LoZ: Ocarina of Time 3D --- abbyhaxxor<3 I always rush here to tell GameFAQs my problems!
Well, as far as must-haves, I guess Luigi's Mansion 2, Mario Kart, Super Mario 3D Land, and Fire Emblem. Personally, I'd also recommend Samurai Warriors, Dead or Alive, and Star Fox. --- If you believe in Jesus Christ and are 100% proud of it, put this in your sig. PSN: DarkJustice77. Wii/DS/3DS codes: Just ask.
3DS: Kid Icarus Uprising Luigi's Mansion 2 Super Mario 3D Land Mario Kart 7 Ocarina of Time 3D
For DS: The World Ends With You Chrono Trigger Any of the Professor Layton games Mario vs Donkey Kong Mini's March Again --- Official nobody of whatever board I post on. NNID: Jason101 3DS FC: 2793-1140-7595