Super Mario Odyssey.
It was EXACTLY what Mario needed after things got stale from the end of the Wii/DS era and throughout the Wii U/3DS era. With the constant stream of NSMB titles and 3D Land/3D World, playing with the similar settings, themes, and tones based on the SMB3 and SMW, and just how frequent they were: 2010 - NSMB Wii, 2011 - 3D Land, 2012 - NSMB2 and NSMBU, 2013 - 3D World. That's 5 games in a 3 year span. Fans were pretty tired of Mario at that point and NSMB gameplay style. They wanted Mario to take a break and then come back with something fresh and different like how it was before.
After the NES and prior NSMB Wii and Galaxy 2, we only used to get one mainline Mario game per console, and it was something different and groundbreaking each time.
The SNES had Super Mario World which is widely considered as one of the greatest games of all time and arguably the greatest Mario game ever.
The N64 had Super Mario 64 which ushered in a brand new era in gaming and revolutionized 3D platformers.
The GameCube had Super Mario Sunshine which expanded upon Mario 64's platforming challengers while also experiment w/ the formula and franchise in unique ways.
And then the Wii had Super Mario Galaxy, an absolute masterpiece that made use of the Wii's motion gimmicks while also leaving an incredible feeling of magic and majesty.
That last point is VERY important, because while Galaxy 2 is also a fantastic game, it was still just more of the same that we got from Galaxy 1. It was retreading old ground. It was still magical and majestic, but on a lower level than the first game because we already knew what to expect.
And then we got the NSMB games and the 3D Land/World duology, which took the 2D formula and put it in 3D. But they were so common and safe that it was almost boring. Like "business as usual." The same old "Bowser kidnaps Peach, Mario go save. Platform for 8 worlds." In some instances, it WAS boring. (Looking at YOU, NSMB2!)
Fans wanted a break from the series for a bit and when it came back, it wanted something fresh. Something different, something ACTUALLY NEW. Not in name, but feel. They wanted that same sense of excitement, magic, and majesty that the series had been sorely missing since Galaxy 1 & 2. Something that you would get playing those old classics from the NES to N64.
And when the Switch was about to launch and we got those first trailers of Odyssey, THAT was the most excited that fans had been in a VERY long time because it looked like we were FINALLY going to get our wish! The original trailer in the Switch presentation and seeing Mario traveling to all these different places like an ACTUAL city, the gameplay looking like it was ditching the 3D Land/World/NSMB style and going back to 64/Sunshine/Galaxy. Then, E3 2017, seeing Cappy and the Capture mechanic, hearing "Jump Up, Superstar" for the first time!
And then the game came out, and it was EVERYTHING we all were hoping it would be and THEN some! An absolute masterpiece from start to finish and yet another title that lived up to the legacy established by many of its predecessors. Mario was back, baby! And by extension, so was Nintendo! After the dark days of the Wii U/3DS era, and the absolute pressure that was on them to make the Switch succeed right out of the gate, this game NEEDED to deliver. Breath of the Wild and Mario Kart 8 Deluxe definitely got the Switch off to the right start, but it was THIS game that firmly cemented the Switch's status as THE gaming thing to have. (Up until the PS5/Xbox Series launch, anyway)
TL:DR - Super Mario Odyssey, on top of being just an absolutely incredible game, is also the game I feel represents the Switch era the best as well as Nintendo bouncing back from its 8th Gen ditch, silencing ALL doubters, haters, and naysayers, and proving ONCE AND FOR ALL, that they are NOT the company you should count out. Because while they may get knocked down (sometimes, by their own doing), they always get back up, and when they do, they come back bigger, better, and stronger than ever.
And that concludes my essay as to why Super Mario Odyssey is the Switch's best first party exclusive.
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