Like its namesake Super Mario Land, it's a passable recreation on inferior hardware.
SML was made inferior by its sequel. Mario 3D Land was made obsolete by modern handhelds that let you play "real" 3D Mario games on them.
That doesn't make it bad, not at all. Mario 64 DS has the same issue. A cool novelty for the time when the alternative was nothing, but now you can play the games that SML/3D Land are copying and thus they're a lot less interesting without that novelty.