what would the the world be like without nintendo?

[Grey Acumen]

console gaming would never have gone mainstream. It would have been a niche of much more tightly constricted genre's and demographics.
The transition to 3d would have been downright painful as other companies attempted to still use the dpad with a 3d environment. It may have even been abandoned entirely.
There never would have been an attempt made for a portable system that actually played full fledged games. By the time anyone attempted to make a portable console, the shift to 3d graphics would already have people expecting them, and so a portable console would only be seen as taking a step back, since it didn't have time to grow and flourish on it's own.
PC games would basically be filling the gap, but they wouldn't be pushing the graphics as hard, and the standard for a game would instead be to make a game run on the widest variety of current specs.
Of course, you'd still never have games like Zelda Mario and Metroid. It's hard to say whether companies with similar games would have even come up with them, or been willing to attempt them if nintendo hadn't been around, or if they would have flourished because of the lack of competition.

still though, the biggest issue would be that I think we STILL wouldn't have fully recovered from the Atari crash if it hadn't been for Nintendo. Companies may have complained bloody murder and still hate them for it, but it was only Nintendo's quality assurance, marketing, and public relations that was able to regain the public's faith in the industry.
Another company might have been able to do it, but I honestly don't think they could have done it as well.