I just calculated the % from the GC/WII DS/3DS era , and altogether the number is around 67% first-second party NIntendo games and 33% third parties .

How many for you?

Every Nintendo related console ever came out I try owning all its Nintendo published games.

It's WAY too much of a hassle for me to calculate percentages but if I had to hazard a guess I would say 70% of my games are 7th and 8th gen Nintendo. Another 20% being Nintendo 3rd-6th gen. The remaining 10% is PC games mostly on steam.

EDIT: OH do you mean how much of my 7th and 8th gen collection is first party?
50% on DS
90% on Wii
50% on GC
40% on Wii U

I'll give you my quick version: A little less than 100% but more than 80%.

Lol you are asking something let me check I'll edit the post later on.

looking for WiiU Wii DS 3DS and GC games now. brb

Edit1

Nintendo DS

When you include stuff like EyeTraining etc as games then I have

16 Nintendo (or 13 without eye/walk/training/etc...")
12 Square Enix
5 Sega
3 Konami
2 Ignition
2 Bandai
2THQ
1 Sierra
1 EA
1 Atlus
1 D3 Publisher

So when we only include real games than I have 13 Nintendo games out of 43 DS games in total which makes it 30%  (
I was just looking at the Publisher logos on the cartridges!)

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Nintendo 3DS
(I also just look at the publisher logos or googled for the publisher e.g. Nintendo in case of Professor Layton which makes it a "Nintendo game")

10 Nintendo
2 Capcom
1 TecmoKoei
1 Namco
1 Sega
1 Ubisoft
1 Activision
1 SquareEnix

So having 10 Nintendo games out of 18 3DS games in total makes it 55.5555555555555555555555555555%.
9 out of 18 and 50% when you dont count Layton as Nintendo. Since there is simply not enough good third party games out there Nintendo dominates this system. (where are all my JRPGs this time????) 

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Nintendo Gamecube

18 Nintendo
3 EA
3 Sega
1 Activision
1 Codemasters
1 SquareEnix
1 THQ
2 Capcom
2 Namco
1 Lucasarts
1 Midway

18 Nintendo Games out of 34 equals 52.94%

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Nintendo WiiU

2 Nintendo
1 Ubisoft
1 THQ
1 Sega
1 Namco

2 out of 6 equals 33.33333333%  (you can almost guess every game I own for WiiU lol) I excluded games like Mighty Switch Force and Trine 2  I just counted  games that are available at retail.

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Wii will take a long time  brb

I'd guess around 60-70%

Yes this is the number of first-second party games I asked.

Third party titles published by Nintendo in occident doesn't count IMO (like Layton or Soul Calibur 2 GC)

On GC it was about 50/50, Wii/DS/3DS about 75%

90% all.

GC - 41%
DS - 72%
Wii - 82%
3DS - 100%
Wii U - 100%