Don't fix what isn't broken.

Except the Gameboy started an entire generation before the Nintendo 64.

Do you not see the issue here?

But if we were to do some quick and dirty napkin math...

Gameboy Colour dropped in October/November of 1998, so if we (incorrectly) assume that all sales From March 1999 and onwards were GBC only hardware units sold... That would place the GBC at 54.3~ million units, obviously we lose about 6~ months worth of sales, but it's close enough as the original Gameboy/Gameboy Pocket continued to sell anyway.

That would then give the Gameboy 64.39~ million hardware units sold.

Data here:
https://en.wikipedia.org/wiki/List_of_best-selling_game_consoles
https://www.nintendo.co.jp/ir/library/historical_data/pdf/consolidated_sales_e1512.pdf

So my idea is (and I am repeating this again... So it's silly to wait for a repeat!) to split the Gameboy and Gameboy Colour up and align the Gameboy to the SNES, Gameboy Colour to the Nintendo 64.

******************

The Switch is the other issue as it can be lumped in with 3DS and WiiU being an 8th gen console.

In reality we didn't have the next Gameboy in the 90's because a) Virtual Boy bombed, that had the been successor if it hadn't b) Pokemon became hugely popular and hugely boosted Gameboy sales. 

However, in the context of the discussion, it might be more accurate to either compare who sold the most systems calendar yearly, or who sold the most systems in the timeframe when a system was launched to the launch of the (same manufacturer's) next system. How dominant the manufacturer or system actually was on it's hayday, or was it. 

I think the best tactic for Nintendo is to pretty much keep following the current path. But, I want them to innovate in hardware as well as software. I generally do not see increased power as enough of a reason to upgrade. I like them to keep experimenting with strange stuff.

Having witnessed every gen since Atari 2600, there is one thing I'm certain about: nothing you do will guarantee back-to-back success. In fact, it's rarely happened in the home console market. So all Nintendo can do is make their best attempt and hope, because in the gaming industry, the winds are fickle.

At this point, take a similar approach as Switch as long as it doesn't lead to stagnant or massive drops in sales with each platform.
I'd love for Nintendo to be more pro-consumer (lower prices and less lawsuits and takedowns for one), but it's difficult to argue that it will help their bottom line, and it won't in the short term.

I picked option 3, but really a cross between several of those things: especially option 2 and 3 while maintaining option 1.
But I think option 2 should only happen if they're inspired, the whole idea of the Gamepad seemed very short sighted compared to the Wii Remotes/motion controls and Hybrid play. of course, they should only add in the new tech if they can carry it in their hardware indefinitely, because I want all games to be playable on future hardware, not just some! ALL games that have ever been on Nintendo hardware in the past, along with a fair chunk of Sega/Sony/MS/Apple/Steam games.

I don't understand why we have to go through such mental gymnastics when we have the yearly sales for gameboy and I provided the source and the numbers based off another user's thread:

https://gamrconnect.vgchartz.com/thread/246545/gameboy-total-lt-sales-breakdown/

for the Gameboy the official shipment worldwide numbers are as follows:

by march 1990 3.93M
by march 1991 8.06M
by march 1992 10.67M
by march 1993 7.80M
by march 1994 7.47M
by march 1995 5.58M
by march 1996 4.16M
by march 1997 7.09M
by march 1998 9.66M
by march 1999 12.99M
by march 2000 17.45M
by march 2001 18.86M
by march 2002 4.70M
by march 2003 270k

True but one thing is constant: the Software sales for Nintendo evergreens. That is probably the key to this question.

We often overlook the software sales when looking at the success of a console but if we even look at gameboy, it's the game experiences that kept it alive despite its limited hardware.

You requested a metric so you could put numbers together. That is your request.
It's your own fault.

I just took it a step further to break it down and make your life easier.

But if you cannot see the issue of grabbing a Nintendo handheld and "combining" it with the sales of a home console that launched an entire generation later... Then there really is no assisting you in this matter.
You need to come to terms with the fact you are messing with numbers... Just so Nintendo loses one less console generation.

I have also provided evidence directly from Nintendo... So using vgchartz shipped numbers is irrelevant, you don't get a more accurate number than from Nintendo themselves, unless you are trying to push a bias.