Before the game's release, the developers advised players not to set their hopes too high for the game's story.
NSMBXGP opens with Mario, Luigi, and Princess Peach taking a stroll out in the Mushroom Kingdom. Bowser glides onto the scene in his Koopa Clown Car, and kidnaps the princess as the Mario Bros. do nothing to prevent the situation. Princess Peach yells Mario's name in the same vocal register and frequency as usual. Bowser flies away, finally prompting Mario and Luigi to chase after him, as if the preceding moments were mere formality by this point.
The basic gameplay is very similar to the previous New Super Mario Bros. games. That sentence is as copied from the Super Mario Wiki as New Super Mario Bros. XGP's gameplay is from New Super Mario Bros. 2.
Due to Microsoft's incessant insitence on adding motion-sensing functionality to the game, the obligatory new flying power-up comes in the form of the Kinect Flower. The power-up lets the playable character that uses it jump in midair when their player jumps in real life. This can be exploited as many times as needed, especially by the more physically fit.
New Super Mario Bros. XGP contains eight main worlds, all of which are mind-numbingly easy for anyone who has touched a controller before to beat. The worlds were said to use completely original themes, which in order are:
As can be seen, despite Nintendo's statements, the worlds are themed in exactly the same arbitrary order as one would expect. When asked about this discrepancy in an interview, series general producer Shigeru Miyamoto replied, "We at Nintendo believe that this world order is truly innovative and creative, a necessary staple of the series—now including all Mario spin-offs. It is certainly not the result of our graphic designers wanting to recycle assets from 2009 for the fourth or fifth time."
There is a single special world in the form of World 9, a stellated decagonal prism in space. World 9 includes the hardest levels in the whole game, which are only unlocked when all of the Star Coins of their respectively numbered worlds are collected. They are technically harder than the rest of the game, but are still among the easiest secret levels in Super Mario history.
Like all of the game's visual assets, the music is still "based on" that of New Super Mario Bros. Wii. This includes the overworld and athletic themes, despite New Super Mario Bros. U and New Super Luigi U having already superseded them. More specifically, the soundtrack takes inspiration from New Super Mario Bros. 2's music. All tracks include the "bah" musical cue, as well as the harmonic "daaaah" instrument used in NSMB2, again reiterating each song's melody as it is played. The soundtrack now contains a new instrument in the form of a man screaming atonally. The use of these cues even extends to the World Map themes, and the title screen and menu music.
The only new track composed for the game is the final boss () battle music, which consists only of the three aforementioned instruments played completely randomly.
Critics generally expressed dissatisfaction at the multitude of recycled assets used in the game, and were harshly critical of the lack of new content. However, the game still recieved a mean score of 8.65/10.