Err... bullshit. There were many alternatives to Nintendo hardwares before 1991. Atari 5200 and 7800, MSX, Sega SG-1000, Sega Master System, NEC PC-Engine, Sega Genesis, Commodore 64... to name a few. This is a very biased and agenda driven point of view created around Nintendo, mostly to antagonize it, rather than tell the truth. Yes, there were some unfriendly practices toward third-parties from Nintendo at the time, the cartdrige manucfaturing and limited titles per year, as Konami had to create Ultra Games to overrule it and Namco and Tengen fought against it, but are very exagerated.
If Nintendo was so "evil" and "draconian" as some try to paint it, third-parties would have left them before Sony. Why didn't they left the NES and went to Sega SG-1000/Sega Master System, instead, if Nintendo was so mean to them? Why did they kept their support for SNES when there were NEC PC-Engine and Sega Genesis competing against it, if they were unhappy? Stockholm syndrome? LOL! This doesn't make any sense.