monster hunter and new leaf are pretty much the only reasons to buy a 3ds, so i hope you get at least one of them
luigi's mansion, super mario 3d land, mario kart 7 are pretty good
new super mario bros 2 is also fun if you don't mind the fact that it's basically new levels for an older game (i don't say that harshly to it, i found it really fun)
i want monster hunter though ;_;
edit: wouldn't recommend getting animal crossing as a first or second game since after a while it locks itself down, it's more to be played in small bursts (in a good way) but when you first get a console that's not really what you wanna do
after you have another game or two though it's a great choice