It's entirely normal to immediately want to play through Fire Emblem: Awakening again after finishing it. I don't know why. Probably to see more character conversations, try different job and team set-ups, or maybe just because that climax and ending were so beautiful that people just want to feel the journey happen again and culminate in that moment.
Depends on what kind of game you're looking for.
Shovel Knight is good, but you may have played that on PC already, and even then it's really not a long game. I think
Kid Icarus: Uprising is a great 3DS game--two fun styles of combat each mission, hilarious dialogue, and probably the best multi-player on the 3DS outside Mario Kart 7. It was made by the same guy who makes the Smash Bros games. However, the controls take some getting used to.
Shin Megami Tensei: Devil Survivor is a neat blend of tactical RPG + traditional JRPG + monster gather game. It's a bit challenging at times, though there is an easy mode. Story's pretty good, though the game is long.
Shin Megami Tensei IV, good traditional JRPG + monster stuff, can get pretty difficult at the beginning, but it's got a good story and fun gameplay. It's even longer than Devil Survivor though, a first playthrough is likely to be 80+ hours.
Those are some of my big ones.
Azure Striker Gunvolt is coming out in two weeks and it looks great if you're into 2D sidescroller shooter-ish stuff developed by Keiji Inafune.
Of course, the one I'd recommend above the rest is
Zelda: A Link Between Worlds, but I'm certain if you have a 3DS you've already bought and 100%'d that
.
You didn't find this one kind of boring? After great tactical RPGs on the 3DS like Fire Emblem and Devil Survivor, this one kind of seemed to play itself. The battles are long, but repetitive; everyone's doing pretty much the same thing.