Pokémon was a good choice
and the 3DS versions (Pokémon X & Y) will be out in October, so it's likely that once you've got your money's worth from White 2, you'll be ready for these. It's most likely that at some point you'll be able to send your monsters over from White 2 to X or Y as well.
Luigi's Mansion 2 is definitely up there as one of the best 3DS games. I admit I have kind of neglected it but that was in favour of the Pokémon Video Game Championships, a holiday to Amsterdam (where I'd rather not take my console) and still mashing it up on Monster Hunter every other day. But it's something I'll definitely be trying to complete between now and Pokémon's release on 3DS. I think everyone who owns this would probably suggest you get it, it's definitely the best first party game of the year from Nintendo (so far).
Super Mario 3D Land and New Super Mario Bros. 2 are both great games, but the latter is something that will feel a bit too 'same-old' if you have played the NSMB games on DS, Wii, or Wii U. However, if you haven't played many of those and have an urge for some Mario retro style, then this won't disappoint. Super Mario 3D Land is a longer game that IMO is something you'll get a bit more out of (unless you take a liking to the Coin Rush mode on NSMB2). It's a very unique Mario game, combining the 2D and 3D styles perfectly. It's so hard to say which you'll enjoy more, so I can only say get both. Maybe one now and then another later in the year - look to get them on the cheap if possible though I doubt it'll be easy.
Carrying on with the Mario theme, Mario Kart 7 (and any other Mario Kart game ever) is probably the game you'll get the most fun (and frustration) out of. It's obviously the best online multiplayer option on 3DS right now and it may well stay that way for the entire existence of 3DS (though I'd wager something like Monster Hunter 4 would rival it). But yeah, Mario Kart is always great if you like a less serious racer. Definitely worth the money.
I'll drop a small note on Paper Mario: Sticker Star as well, but this won't be for everyone. It's basically Mario in RPG form and the previous instalment in this series (that kept the same formula) was one of my favourite games of all time - Paper Mario and the Thousand Year Door on the GameCube. In all honesty, Sticker Star does not match up to it as well as I'd have hoped, but it's still a good game. The comedy in it is great and the gameplay is something I enjoy. I just find it almost impossible to catch everything without using an online guide though. I've tried my hardest but you will just be walking around aimlessly looking for something you missed. I guarantee it. If you can get past this lack of direction and you're an RPG fan, it will probably win you over. But it wasn't quite as good as I'd hoped.
The only other games I own at the moment are Professor Layton and the Miracle Mask (great instalment, but only play it if you have played the others), Monster Hunter 3 Ultimate (my favourite game at the moment, but much better value on Wii U with online play), and Resident Evil Revelations. I won't say much more about the first two as you you'll probably be best finding a pre-owned version of an old Layton game first and Monster Hunter, while great, is something that's not for everyone and takes a lot of time out of you (and is so much better with online multiplayer that I'd argue it's not worth buying the 3DS version unless you have a good few friends with it locally). Resident Evil, on the other hand, is something that really brings the series back to it's high point for me. It is true survival horror. The kind of game we grew up with on the PlayStation, none of this fast paced shooter action like every other game in the world. That might just be me, but it looks beautiful and feels a lot more scary and compelling that the latest Resident Evil games. Again though, however, it has recently been ported to Wii U, PS3, and 360 so those versions could surpass it (more-so the Wii U version due to second screen GamePad features).
As for games that I don't own (so my opinion barely matters), there's: Fire Emblem: Awakening which is hitting all the heights right now. Zelda: Ocarina of Time 3D, something that everyone adores. Kid Icarus: Uprising that I've not touched but have heard great things about. Donkey Kong Country Returns 3D, I had this on Wii and it was great - guessing it's much of the same on 3DS. Animal Crossing is also out on Friday which I'm anticipating highly, but this is another game that won't be for everyone.
I've missed out a lot of great none-first-party games here, so hopefully someone else can touch upon those. But in general, most people tend to buy a Nintendo console for Nintendo games, so I thought I'd get those out of the way first ;D
