Well I would also suggest Kid Icarus: Uprising.
The online mutiplayer mode is fun to play with people.
That is not a fighting game at all.
This is becoming ridiculous:
"Q: What's the best 3DS RPG Game?
Fan Boy: Kid Icarus
Q: What's the best 3DS Action Game?
Fan Boy: Kid Icarus
Q: What's the best 3DS Adventure Game?
Fan Boy: Kid Icarus
Q: What's the best 3DS Racing Game?
Fan Boy: Kid Icarus (when you get a gear)
Q: What's the best 3DS gay-angel Game?
Fan Boy: Kid Icarus"
I really like my Kid Icarus game, but calling it a fighting game is the same of calling Rayman a porn game.
Now on topic. I have Street Fighter 4 and Tekken, but I've never played DoA, so, I suggest street fighter.