Nintendo isn't indispensable for the industry, but if 1 of the big 3 were to perish, Nintendo's bankruptcy would cause the strongest effect.
Nintendo isn't the only one who innovates, but out of the big 3, they innovate the most.
the term"Best games" is subjective, but lets just say, there's a reason why it's mostly Nintendo games that are the highest rated in each gen (barring the 7th gen, but who'd put GTA IV over Super Mario Galaxy?)