So it's a bit like a group of people calling something "THE BEST _____ OF ALL TIME", but it would actually be pedantic to call anyone out on this whenever the newest best thing of all time is declared. Hyperbole is everywhere.

85% of the handheld market is a pretty big deal.

The PS2 accounted for about 75% of the console market during the sixth generation, and many of its sales came well after its competitors were discontinued and all of their successors launched.

That's not the important thing of why I quote you, but no problem :)

Relative to other companies in the industry, I would say that yeah, Nintendo is THAT important. They practically own the market of a few genres. Where would 3D platformers be without Nintendo? No other company is really looking at 3D platformers seriously. Ratchet and Clank is nowhere near where it used to be in and other than that, there are very few mainstream games in this genre. You could argue that Nintendo sustains the karting genre and the Brawler genre (Smash Bros). Even thinking about their games like Legend of Zelda or Metroid Prime I don't see other companies making similar games.

Compare this to say, Sony's first party offering (let me state before I get into this that I am not dismissing the quality of these games). I will steal a list from someone else in this thread:

Action adventure - Uncharted/ Ratchet & Clank
Racing - Gran Turismo/ Motorstorm/ Wipeout/ ModNation Racer
1st Person Shooter - Killzone/ Resistance
Shooters - M.A.G/ Starhawk/ Socom
Action - God Of War/ inFAMOUS/ Twisted Metal
Platforming - LBP/ Sly Cooper
Sports - MLB:The Show

Where would each of these genres be without Sony? Racing would be totally fine, Sports games wouldn't suffer, Nintendo can (and pretty much does) hold up platforming by itself, we all know shooters wouldn't suffer. I wont talk about all of these games because I haven't played games in all of these franchises but it feels to me like other companies make games in a space that holds a lot of other great games. Compare this to how Nintendo makes games in genres that feature almost nothing except for Nintendo games and when other games enter the genre, they are always compared and almost always come up short (not always mind you...).

Nintendo is a huge player in the industry and the industry would suffer without them. We would still get a ton of great games from other companies but we would be missing a piece of what makes this industry great (many other companies also contribute to this). Saying Nintendo isn't THAT important seems quite silly to me, like you are trying to bring them down for no apparent reason and like you are only comparing them to some ridiculous standard set up by who knows who. On almost every level I can think of, Nintendo is THAT important.

Did you mean that because I'm a Nintendo fan, it's expected that I'd say they make the best games?

if that's the case, you can say that for absolutely every game in existence, or hardware for that matter.

Say Sony stops making consoles and after a void, Apple, Samsung, Google or whatever comes with another console. If that's your perception of something not being important then anything is not important in life, because practically everything can be replaced.

It's fair that that's your opinion. I just get an itch when I see absolutes applied to subjective views because it basically gives them the force of fact; there's no opportunity for middle ground.

When you say "Nintendo games," do you mean that collectively, or individually?

Not necessarily, but actually that's what you said in the first place. It helps to point out that the op is right in the third affirmation.

I feel like I kinda need to put a disclaimer in my sig, that any view I express is simply my opinion and I do not claim it as fact. XD It was not my intention to express it as an objective absolute.

I mean both the average quality of their output, and the amount of all-time greats they develop.

That was more or less the point. That there isn't anything that makes Nintendo immune to that.