Well...kind of.

Take GTA for example. They probably have a huge install base. If they didn't, then it would be an extremely stupid move to have a hollywood-movie budget for their games.

Now, take a game such as FNAF, you don't need a HUGE install base. Scott Cawthon did though, and had an amazing experience for what a large install base is.

He probably would have needed a few thousand people for an install base, but got millions. He was a good example of when an install base rarely needs to exceed the thousands.

GTA could work on a smaller install base. What the larger one allows. Is the music costs. Half the games budget is definatly for the radio's music. Rabid fans also help. Because they'll be the ones who rebuy the game 3 times. When the game was released on the 7th, 8th gen's. And PC release.

Depends on the topics people is discussing.

A few franchises definitely are stagnating, and there's no denying that.  But many others are held back because of their ties to Nintendo hardware.  Even going as far back as N64, Nintendo has had great games on their systems yet has been up against a rival system that many gamers consider to be a better value.  I'm of the opinion that many of them wouldn't be stagnating if every game was available to everyone.  Even a person who's never bought a Nintendo system in their life might find a couple of Nintendo games they want per generation, but they never do/will.

It may not be differences of 5 million, but it does have a large impact..

There will be more sales for games if there are more consoles.. if you don't own the console, you won't get the game, and I know many people that want to play games like Smash, Mario Kart and Bayonetta, but they don't own the Wii U so they don't buy it

Its not a few, its the majority of Nintendo's long standing franchises. So which peticular Nintendo IP would sell drastically higher if Nintendo were to go 3rd party?

Is Kirby going to sell over 3 million on PS4/XB1? Probably not. Is 3D Mario going to sell much more than 12 million on PS4/XB1? Probably not. Is Animal Crossing going to sell over 12 million on PS4/XB1? Probably not. Is Metroid going to sell much more than 3 million on PS4/XB1? Probably not. Is Pokémon going to sell much more than 15 million on PS4/XB1? Probably not. Are Mario spinoffs like Paper Mario, Mario & Luigi, Mario Sports, Mario Party going to sell significantly more than 3 million on PS4/XB1? Probably not. What about Yoshi, Donkey Kong, Fire Emblem, Pikmin, etc, will they show significant growth on PS4/XB1? Probably not.

It's likely that only a few franchises would show any notable growth.

Astounding is the difference between Red/Blue/Green and Diamond/Pearl. 31 million to 19 million even with a bigger userbase?

Pokemon is selling what it usually does. It's not a 20 million seller, it's a +10 million, maybe +15 million seller. Specially considering it now competes with smartphones.

I stated in the OP that I'm specifically talking about Nintendo IP in response to people saying they would do much better as a 3rd party publisher/developer. Most of Nintendo's franchises seem to sell a pretty consistent amount regardless of the install base which leads me to believe most Nintendo IP wouldn't have a very significant increase in sales by releasing on Playstation/Xbox.

Considering Bayonetta did rather poorly on a combined install base of over 160 million, it's pretty safe to say that game isn't very dependant on install base.

But I'm talking about the majority of Nintendo IP which have historically sold pretty consistent amounts regardless of install base, their are only a few examples of games that don't follow this trend.

Oh sorry i thought it was about multi plat games my bad