80's Nintendo lol.

Which did come out on Wii later in the decade on Wii Virtual Console, so still a 2000s game internationally technically lul

Easy choice for me: 2000s.  The lowest point in Nintendo's gaming history is probably 2010-2016 which is most of the 2010's.  It's only 2017-2019 which makes this decade seem good.  Meanwhile I think the Wii, GBA and DS were all great systems (in that order).  The Wii, in particular had some of Nintendo's best first party output: Wii Sports & Resort, the return of 2D Mario, Excitetruck/bots, Punch Out Wii, etc....  The virtual console was an awesome idea, which they never should have abandoned.  Motion controls were really fun (in the right games).

The main thing I want out of gaming is experiences that I've never had before, and with the Wii was an entire console about delivering original experiences.  I want more of this from Nintendo.

I actually thought 2010 was a great year; we got one of the all time greats in Mario Galaxy 2, plus Sin & Punishment 2 in the West, Kirby's Epic Yarn, Donkey Kong Country Returns, Pokemon Heart Gold/Soul Silver, etc.

Easily and without a doubt 2000's Nintendo. 

For the Wii's 2010 and on games, we are looking at...

https://www.nintendolife.com/games/browse?system=wii&year=2013%2C2012%2C2011%2C2010&score=10%2C9%2C8%2C7

DKC Returns
Galaxy 2
Kirby's Epic Yarn
Sin and Punishment
Tatsunoko vs Capcom
Monster Hunter Tri
The Last Story
Skyward Sword
Xenoblade Chronicles
Kirby's Return to Dreamland
No More Heroes 2
Rayman Origins

For the DS's 2010 and on games, we are looking at...

Heartgold/Soulsilver
Solatorobo
Pokemon Conquest
Pokemon Black
Okamiden
Pokemon Black 2
Dragonquest 9
Dragonquest 6
Infinite Space
999
Alien's Infestation
Ghost Trick
Professor Layton and the Unwound Future
Rune Factory 3
Professor Layton and the Last Specter

For 2010's Switch we have...

Odyssey
BotW
Xenoblade 2
Smash Ultimate
Octopath
Dragonquest 11
Yoshi's Crafted World
Poke'mon Sword
Witcher 3
Luigi's Mansion 3
Link's Awakening
Fire Emblem 3 Houses
Astral Chain
Mario X Rabbids
Ys 8
Splatoon 2
Bayo 2
and a whole bunch more 3rd party games, but who are we kidding? Switch from 2020-now drowns all those 3rd party games out with even more 3rd party games. 

We already know what the 3DS and Wii U had since they were both limited to that decade. 

Now for 2000's GBC we have...

Poke'mon Gold and Silver
Shantae
Metal Gear Solid
Oracle of Seasons/Ages
Warioland 3
Mario Tennis
Megaman Xtreme 2
Toki Tori
Master Blaster Enemy Below
River King 2

For 2000's N64 we have...

Sin and Punishment
Paper Mario
Kirby 64
Majora's Mask
Conker
Perfect Dark
Pokemon Stadium 2
Banjo Tooie
Mario Tennis
Ogre Battle 64
Excitebike 64
Star Wars Battle For Naboo

For 2000's Wii we have...

NSMB
Mario Galaxy
Super Paper Mario
Brawl
Punch Out
Metroid Prime 3
No More Heroes
Klonoa
Fire Emblem Radiant Dawn
Muramasa
Little King's Story
Zack and Wiki
Trauma Center 2nd Opinion

For 2000's NDS we have...

NSMB
The World Ends With You
Knights in Nightmare
Phantom Hourglass
Bowser's Inside Story
Final Fantasy IV
Mariokart DS
Spirit Tracks
Professor Layton and the Curious Village
Dawn of Sorrow
Might an Magic
Sonic Rush
GTA Chinatown Wars
Mario and Luigi Partners In Time
Phoenix Wright
Metal Slug 7
Valkyrie Profile
Poke'mon Diamond
Professor Layton and the Diabolical Box
Suikoden Tierkeis
Portriat of Ruin
Advance Wars Dual Strike
Rune Factory
Advance Wars Days of Ruin
Kirby Canvas Curse
Starfy
Ninja Gaiden Dragon Sword
Final Fantasy III
Elite Beat Agents
Contra 4




That's 44 2010 Nintendo games that overflow into either the previous or next gen's console. 

And 64 2000's Nintendo games that find themselves straddling decades with the Wii, GBC, DS or N64. 

It's already a blowout for 2000's Nintendo and I haven't even thrown in Gamecube or GBA. Please don't make me type more. Im tired. 

I pick the 2000s.
While the N64 and Gamecube didn't exactly set the world on fire, Nintendo absolutely killed it in the handheld space during that period. The Wii and DS were monsters in terms of software and sales.

On the other hand, 2012 to 2016 were probably the worst Nintendo years... ever. The Switch somewhat offsets this, but I just can't shake off the bad feeling of those years. It's kinda like COVID poisoning the 2020s, no matter how good the second half is going to be lol.

2000's wins, mostly because the 2010's had a weak middle section.

This is a tricky one for me; I wasn't a big fan of the Gamecube, but I did love the N64 and Wii, and the 2000s did bring some of my favourite Nintendo games like Mario Galaxy, the Metroid Prime trilogy, and Twilight Princess.

On the other hand, while the Wii U years do drag down the 2010s somewhat, they also saw the Wii's strongest year as well as the Switch's explosive arrival, delivering many games I absolutely loved like BOTW, Mario Galaxy 2, Mario Odyssey, Tropical Freeze, Mario Kart 8, Xenoblade and Splatoon.

Tough call.