I'm a major Nintendo fan but if Nintendo didn't enter gaming we would be in a Sonic centered universe. Sonic would have replaced Mario Atari would probubly still be alive as a console manufacturer. Sony would have never entered the market, neither would Phillips, Apple and Microsoft would have continued to support games as a medium for computers.
Alot would change , alot of the great games we see today were inspired by Nintendo's titles. But I think Sega would have filled the void with Atari surviving to be the secondary console of choice. Computer gaming would have probubly been a much bigger challenge to the console centric sociaty we have today.
Can you imagine a world where Sonic went unchallenged by Mario.
Now the real question has to be, would gaming have survived without Nintendo or Sega? Could Atari single handedly have survived the crash and come out prosperous. Or would the world give up on console gaming altogether?
I think if it wasn't for both Nintendo and Sega , we would all be gaming on our PC's and/or Mac's and the graphics would probubly be N64-PS2 visuals right now instead of the next gen stuff we have. No competition would have existed to push the gaming technologies we enjoy today!