I'm not mentioning anything Mario-related, because if you're interested in Mario, chances are you already have those titles or they're in your sights. That, and I cannot care about Mario anymore as I've had a literal lifetime of Mario exposure.
Also, no ports, remakes or retro games.
-Fire Emblem: Awakening
It isn't THAT great (when you look past the glimmer and polish, it's pretty shallow), but it's not bad.
It's still one of the best non-Mario, original titles on the system.
-Monster Hunter is Monster Hunter. You've played one, you've played them all give or take a couple of features.
Now that I've had a chance to try it...yeah, it's still Monster Hunter.
-Luigi's Mansion is pretty good.
-Kid Icarus Uprising is a WEIRD game. What it does well, it does amazingly well, and what it does poorly drags the game down.
More than any other game, Kid Icarus: Uprising made me regret getting a 3DS.
Not because it's a bad game (it's not), but because it highlights every major weakness of the 3DS's design.
1) Stereoscope-3D is gimmicky shit and a hallmark of a LOT of wasted effort.
2) 3D camera controls (that is, gameplay that moves in 3 dimensions) are fucked on a system lacking two analog buttons.
3) GOOD games that use a 2D plane are rare outside of the retro library, exacerbating flaws 1 and 2.