No problem, honest mistake

For a Nintendo IP.. maybe not that important because an IP can be successful on a fairly small install base. Success is however relevant.

From a business perspective the install base in very important, it's the difference between making relative peanuts (Wii U) vs printing money (Wii).

While I see your point and to a degree you do make some sense, ALL businesses involved in mass market production will prioritise the install base because that is where the real money is.

The issue with this argument is that the Wii's were still in the households. Nothing was preventing people from playing the hardcore Wii games on their family's Wii. You can't sell 101 million platforms for there not be access to hardcore gamers of said platform.  

Not exactly. Most of the profits come from software not hardware. Additionally Nintendo's consoles, even when they sold little, were still selling for a profit. Selling more platforms gives you a market advantage and raises the potential for profit, but it doesn't necessarily mean you'll be more profitable. Just compare the Gamecube with the XBOX and PS2. 

Yep obviously any hardware manufacturer wants to have the biggest possible install base but my argument was mostly against people who think Nintendo would be better off going 3rd party as Nintendo would no longer make money from hardware & accessories, they would no longer receive royalties from 3rd parties and they would have to pay royalties to put their games on other companies hardware so their games would need to sell a lot more than they do on Nintendo hardware and as we have seen, most Nintendo IP don't grow proportionally to the size of the install base so I don't see many games having very significant growth by being playable on competitors devices.

In my opinion what is important isn't purely install base, but rather an active install base. For example, an excellent - must buy game could be exclusive to the PS2 today, but its sales will be very limited, despite there being tens of millions of PS2's circulated out there. Why? People have put their PS2's in the closet/attic and its a hassle to get it out, dust it off, and get it in working condition. Many more don't have PS2 games on their radar anymore for the sole reason that they are PS2 games. This was true for the Wii at the end of its life. Many people moved on to other consoles/PC's, and there was a decline in Wii software sales because of this. The Wii U is an example of a platform with a high attach ratio. Why? The Wii U sells to people who are enthusiastic about it. 

If I had a Wii U I would spend all day playing MK8 and Smash but I'd never shell out the cash for one for a reason unknown to me, I just can't really do it.

That really has nothing to do with what I said in the OP.

It's talking about going third party, if they went third party people like me would buy more of their games.

Unless I'm mistaken?

I said in the OP that there are a few Nintendo franchises whose success can be linked to install base, games like Mario Kart & Smash Bros are two of the titles I had in mind. I'm mostly asking about Nintendo's portfolio as a whole, will things like Kirby, Yoshi, Metroid, Fire Emblem, Donkey Kong, Mario Party, Paper Mario, Mario Sports, Pokémon, Pikmin, Kid Icarus, Fossil Fighters, Rhythm Heaven, WarioWare, Xenoblade, Punch-Out, etc show significant growth by being on Playstation/Xbox?

Like I have shown in the OP and in subsequent posts, many of these franchises seem to sell a similar amount regardless of how well the hardware sells which is a pretty big sign that these games won't see that much growth simply by being on competitors devices that have bigger install bases. Does going 3rd party as a whole benefit Nintendo or would we basically see a select few titles show massive growth while the rest remain stagnant? Does the growth of these select few titles outweigh the fact that Nintendo no longer makes money from hardware, accessories, 3rd party royalties while also having to pay royalties?