A 3D Mario only ever launched with two Nintendo platforms, and the second time it was a remake.

3D Mario games have been absent from Nintendo launches not because they're not big but because they take some time.

Nintendo might have a new Mario Kart ready by launch but it's hardly necessary and they need to focus on the experience first and making it to launch of Switch 2 second. 

3D Mario and Metroid Prime 4 (even with no other first-party titles) would probably already be better than just about any first-party launch line-up in Nintendo history. Switch had BOTW (a cross-gen game, but a massive one) and 1-2 Switch (a middling game to most). 

I’d love to see Xenoblade Chronicles X dx (XCXDX) or a sequel, and I think there’s a good chance of that at the end of year 1.
Super Mario Kart 9 and in the 6 month window.
The next 3D Mario seems a lock for launch day.

My moonshot game would be Xenogears Remake by Monolithsoft, licensed by Square Enix, published by Nintendo.
Written and Directed by Tetsuya Takahashi
Story: Soraya Saga/Kaori Tanaka
Music Composition: Yasunori Mitsuda
Art Director: Yasuyuke Honne
Character Designs by Tanaka and (optional) Tetsuya Nomura
Level Design and Map: Koh Arai
(Optional) Script: Masato Kato

I think it’s important to get most of the original creative team onboard, luckily, almost all of the creative minds work at Monolithsoft or have great relations with them. Tetsuya Nomura is someone who I think would be interesting to put on the team, and I know he has good relations with Monolithsoft - he was almost a part of Xenogears but was put on FF7 (which Xenogears was at one point).

Would rather it was a new Donkey Kong Country, but it's more likely to be Mario Kart X.

Depending on when Switch 2 launches, Donkey Kong could still come to Switch first. The theme park area is scheduled for Spring 2024 (Q2 then) and what better way to celebrate than have a new DK game within 6 months of the opening.

On the other hand, considering that it's pretty likely that Switch 2 is coming out Q4 2024 or Q1 2025, that would still be recent enough to save DK for the next system. 

The Switch had Breath of the Wild AND Mario Kart 8 Deluxe as basically its launch titles, MK8 DX came out only a few weeks after its launch. Mario Kart was absolutely a huge part of the Switch's early success and it's been a big part of its success ever since. 

3D Mario and Metroid is not going to match up to that. And Switch got Splatoon 2 not soon after and then it's own 3D Mario as well all within its first 9 months or so. So Switch only having a 3D Mario compared to Switch 1 having 4 of those big hitters ... that's a pretty far drop off. 

Switch 2 is already going to be at a fair disadvantage over Switch 1 by not having a Breath of the Wild type Zelda launch title, not having Mario Kart there would be a mistake IMO. 

Mario Kart is Nintendo's Grand Theft Auto, it's by far their biggest franchise, even 3D or 2D Mario don't compare sales wise anymore, Mario Kart 8 Deluxe has outsold Mario Odyssey + NSMBU + Mario 3D World on the Switch combined, it will outsell Mario Odyssey + Mario Wonder combined as well most likely. And it will drive NSO revenue more than any other Nintendo game thanks to DLC. Switch is the 3rd straight Nintendo system that Mario Kart has been the no.1 seller on too (3DS, Wii U, Switch), so this isn't some outlier one off, this is a definite trend that's been ongoing now for 10+ years. 

If any big Nintendo franchise is overdue for a new console installment it's Mario Kart. The last new console game in the series will be 10 years ago next year. Even the mobile game released now over 4 years ago. 

I said this many times but Mario Kart for the next Switch should have been in hard development starting in 2021 at *the latest* (planning should have started a year before that at least). That should have been priority 1 at Nintendo once offices opened up again post COVID. They should be nearing 3 years of hard development of this game (2021, 2022, 2023). 

It's not like you even need 60 courses to launch with, 12-16 new courses + 12-16 remixed old tracks would be enough to launch the game with and then you can add DLC as you go. 

Odyssey has proven that 3D Mario sales are nothing to sneeze at when it's such a quality title. It's no Mario Kart, but not even a new Pokemon game's sales can touch Kart today. A brand new 3D Mario game that is demonstrative of the new system's capabilities would be a great launch title, and it surely wouldn't be Nintendo's only game for the fall.

Honestly, I'm not sure Switch 2 necessarily needs Mario Kart on launch day. I can only imagine the level of shortages we'll see for Switch 2's first holiday. Having your alpha title come out when the system is at its most difficult to find could prove to be less effective than launching it several months later when the install base has grown a bit, the system is more readily obtainable and the anticipation has grown even more.

It’s interesting you bring up extending the ending since this is what I was thinking as well and have seen others also bring up. I think the game lends itself really well to something further happening after that ending, so it’s a good route to explore for a remake 

Regarding Pokemon, it was VERY clear gf had no ability to develop for a console like Switch in such short dev times this gen. Add a far more powerful hardware into the mix when they still don’t even know how to develop for home consoles circa 2008, and it will be a disaster if they don’t take their time with the next game (gen X). I think Nintendo is well aware of this now as well and won’t let them pump out broken garbage for the next Switch either.

S/Vs sales were extremely concerning in how massive it opened and then cliff dived. The reception definitely hurt. A game like that launching on a console with a mere fraction of the install base S/V launched on could be an outright disaster for the franchise. Nintendo’s not gonna let it happen. Why I say 2027 for Gen X and in the meantime we get Gen V remakes along the way by a different dev

Edit: posted twice 

Where is the information regarding DK game? Is it the opening of Donkey Kong Country in Universal Studios Japan?
We could be hit with a DKC4 for Switch and a 3D DK for the NG, same year.

-Grezzo's last game was Miitopia in 2021. They are usually involved in Legend of Zelda remakes. So we could be seeing a (very unlikely but I can dream) a Legend of Zelda All Stars featuring Legend of Zelda, Link to the Past, and Oracle of Ages/Seasons.

-Camelot's last game was Mario Golf Rush in 2012, and pump a game every 3 years. I was speculating a Mario Baseball game (Baseball is a bug Japanese and American sport).

-Pokémon won't be porting any games to both consoles, they can barely make things run on the Switch. I think they'll be pushing for the NG. It will either be Let's GO Johto or Gen 5 remake. I hope for Let's GO, that way they can spend more time on gen 5, I can't let them be massacring my boy like gen 4 remakes.

-Mario Party gets pumped out every 2 years. The last one was Mario Party Superstars in 2021. And a lack of Mario Party in 2023, means 2024 is most likely to arrive. Either Switch or NG.

What is Xenogears? Iv'e never heard of it, but it sounds rather stacked.