Based on what you've said, you'd probably want Star Fox. It didn't really add much, but it does have much better visuals, and an improved multiplayer mode (though it's local-only.)3D Land is basically a 3D version of NSMB. It's 3D, but it plays in short stages like the 2D Mario games. A fun game, but it certainly doesn't have the charm that SMB3/World had.
You should go for SM3DL because it's at least a new game to try out. SF64 will be the same thing you've played before.
An enhanced port or an original 3DS game. Your choice!
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