I think it will be a multitude of titles coming back. Nintendo pulled out many guns from its history over the past 7-8 years, and I don't see that aspect changing. I think it's something they are going to utilize even more.
Advance Wars 1+2
Another Code
Mario Strikers
Mario Golf
Mario vs. DK
Mario & Luigi
Super Mario RPG
Paper Mario: Thousand Year Door
Zelda: Link's Awakening
F-ZERO 99
Famicom Detectives
Metroid Prime
Pikmin 1 & 2
DK Country Returns HD
Kirby Return to Dreamland
Pokemon Let's Go
Pokemon Diamond & Pearl
Pokemon Mystery Dungeon
Are all games that either received a remake/remaster, and/or a new entry after more than 10 years. Over 20 games just from Nintendo, not even including everything brought over from the Wii U library.
The Switch 2 is upgrade is likely to be the largest jump in visuals for Nintendo since N64 to GameCube. It's a substantial difference, larger than Wii to Wii U due to the tools and lack of confusion regarding the hardware.
Taking the place of the kind of growth Wii U titles helped give the Switch, it's likely Nintendo could utilize a massive array of classic titles and upgrade them for a new generation. The rumored inclusion of pointer controls making a return only helps this notion that, they are looking into their past libraries.
So what games make a return?
Punch Out NEW
F-Zero NEW
Eternal Darkness remake
MGS: Twin Snakes Remaster
GEIST reimagining
Wave Race NEW
EXCITEbike/Truck NEW
Duck Hunt NEW
Zelda Remake
Star Fox NEW
Sin & Punishment
Mario Baseball NEW
Mario Galaxy 2 remaster
I think about 30% of these are... Likely.
Knowing Nintendo, I think we also see a return of a couple long dormant franchises like Mach Rider or Golden Sun.
I think Punch Out, Duck Hunt and/or Sin & Punishment are most likely for a year one game. Racing games like F-Zero or Wave Race spread out in a 2 year basis from Mario Kart 9. A Zelda remake will likely hit in 2026 or 2027, to make up for the long wait from Tears of the Kingdom.
Star Fox after 5 years, Mario Baseball 2 years after launch, Mario Galaxy 2 would be a year or 2 after new Mario Game.
Games like Eternal Darkness, MGS: Twin Snakes or GEIST could first hit in 2026 and spread out every other year.