The wii was unstoppable in its first few years. The console was flying off the shelves. I know most were buying it for wii sports, but nintendo went ham with the first party lineup as well.

Also, during the first year of the Wii was when Nintendo bought Monolithsoft. The studio responsible for Xenosaga, born from the development team of Xenogears, which in turn was made up of developers from Final Fantasy 6 and Chrono Trigger.

Don't forget Actraiser!  Game concept shouldn't have worked, but it was fun as hell.  But I think the first 12 months following the SNES launch were the best 12 months in gaming period.  I really didn't even expect Super Castlevania IV and Final Fantasy IV to be as good as they were.  Final Fantasy IV blew my mind.

NES is weird, because it also had a soft launch in the US.  It was NYC only in 1985, and only in major cities in 1986.  In 1987, it finally went nationwide, which is when I first experienced it.  If I can count 1987 as the launch year, then NES wins, but that is actually 4 years after the original Famicom release in Japan.

Similar things happened throughout Europe. Certain cities got the console way before most places did. And pricing was wildly different; although, that may have been childhood me not understanding exchange rates.

I would definitely say the Wii. That first year launch lineup really helped the system's sales explode for the first few years. Even though most bought it for games like Wii Sports, Mario Galaxy, Twilight Princess, Prime 3, etc. definitely helped! Wii Fit also technically kind of fits into that first year slot as well.

N64 would be a close second. Mario 64 & Mario Kart 64 were huge. N64 was outdoing both Saturn & PS1 in its first year. They weren't able to keep up momentum because games like Banjo-Kazooie and OoT were pushed from 1997 to 1998.

It's the Super NES I think. People aren't properly accounting for not only the 3rd party games it had but also the fact that many of them were exclusive to the SNES.

Street Fighter II on the SNES isn't just "ho hum, a fun game to play!" ... you're talking about the biggest 3rd party game of that time, it would be like the Switch 2 getting GTA VI exclusive in its first year.

Super Mario World
Pilotwings
F-Zero
Sim City
Mario Paint
Legend of Zelda: A Link to the Past
Super Scope 6
Street Fighter II
Castlevania IV
Contra III
Final Fantasy IV
Actraiser
Top Gear
Super Adventure Island
Super R-Type
John Madden Football

Ninja Turtles: Turtles In Time, Super Ghouls N' Ghosts, The Legend of the Mystical Ninja, Joe & Mac, Romance of the Three Kingdoms II, etc. also. 

Super Mario Kart also just misses the cut off here by like a week, it release Sept. 1, 1992 which was just barely a year over the Aug. 23, 1991 SNES release date. That's so close I almost consider it a first year game.

So, thus far for Switch 2's first year they have:

- Mario Kart World

- Donkey Kong Bananza

- Kirby Air Riders

- Metroid Prime 4

- Pokémon Legends Z-A

- Hyrule Warriors: Age of Imprisonment

- Cyberpunk 2077

- Split Fiction

- Street Fighter 6

- Elden Ring

- Borderlands 4

- Final Fantasy 7 Remake

- Hitman: World of Assassination

- Daemon x Machina: Titanic Scion

- Kunitsu-gami

- FAST Fusion

Definitely one of their stronger first year console lineups already, and there's probably plenty more yet to be announced for later in the year.

Focusing on the first years in just Japan:

1. NS: The actual launch day was largely underwhelming, but between Breath of the Wild, Super Mario Odyssey, Mario Kart 8, Splatoon 2, and many other classics, there was something for everyone this first year.
2. GC: An amazing first 3 or 4 months, but it petered out a bit in the second half of the year. Still, a large portion of the GameCube's greatest hits came out in this era.
3. Wii: Wii Sports, WarioWare, and Twilight Princess at launch started strong, and although there were the ocassional gaps in 2007, you still had Super Mario Galaxy, Fire Emblem, Super Paper Mario, Resident Evil 4, Mario Party 8, Mario Strikers, Resident Evil Chronicles, Wii Fit, Mario & Sonic, and some popular Naruto and DBZ fighters.
4. SNES: Not only do you have Nintendo classics like Super Mario World, F-Zero, and arguably Link to the Past (it released exactly one year after launch), you had big third party hits like Actraiser, Final Fight, Super Ghouls n Ghosts, Mystical Ninja, and Final Fantasy IV. Problem is, a lot of the support was still on older hardware at this point. In 1991, Nintendo was also supporting NES, Game Boy, and even Game & Watch.
5. Wii U: This one is weird. It is not considered an amazing lineup, but you had a large library at launch, two Super Mario games, Pikmin, Monster Hunter 3 Ultimate, Wind Waker HD, and Wii Party U.
6. N64: An anemic early lineup, with months-long gaps between releases at points. At least you had the twin colossi of Super Mario 64 and Mario Kart 64, along with Star Fox.
7. NES: Only 16 games were released on the Famicom its first year on the market, with literally no third party support. When people talk about the best NES games, they usually aren't referring to Donkey Kong ports, Mahjong, Golf, and Baseball.