Probably Playstation. To me the question needs to be viewed backwards. If any one console hadn't happened, what would be different today? Playstation crushed Sega, took all of Nintendo's 3rd party support, and probably drew Microsoft into the market the following generation. Absent Sony, Nintendo and Sega were both faltering to an extent, it is possible the overall market would have declined, and maybe the market would not have reached the same mass market level.
NES is probably second.
that's just absurdity. that argument would be like saying the DvD player in 2000 was more significant than the first ever created film projector for theater entertainment just because it potentially brought movies to more eyes and popularity. A fallacy in logic
not only do you not have the Playstation 1 without the systems that preceded it, but you don't even have Sony in the video game market without Nintendo being their first (hence their attempts to collaborate with Nintendo after the giant steps of the NES). And it's not even like the Playstation itself was particularly innovative- it wasn't the first analog stick and there had already been a number of CD video game systems at the time (Sega CD, Turbo CD, 3Do, etc.). Again, streamlining something that's already been created is not more relevant imo
The Playstation 1 was successful in streamlining gaming further, yes, but after the market/hobby had already exploded. Sorry, but making video games even more popular in the target audience of young adults is not that remarkable of an accomplishment in itself
The reality is the video game market was inevitably heading into the direction of getting larger and larger as technology progressed and we entered an internet age. If the PS1 didn't exist then almost certainly someone like Sega (or even Nintendo) would have picked up the reigns where the PS1 no longer existed, because obviously CD based games were already a thing and going to be pushed even more. It's not as if the players who filled the backbone of the PS1 library would have magically disappeared and stopped making games (cough Squaresoft, Enix, Konami, Capcom, etc.)
Anyone picking the PS1 is just out of touch with reality. The most difficult thing you could ever do is essentially create (or relaunch) a dead industry and create the fundamentals for it that would ensure it's survive. the NES in its quality, controller, game library and revolutionary mechanics (save states, D pad, etc>) alone is far beyond what any other system has achieved in terms of relevance on the industry
I mean before the PS1 there were a plethora of systems that in some respect made video gaming popular in public opinion. NES, SNES, Gameboy, Genesis, Game Gear, Master System, 2600, etc., The PS1 used CDs, had a solid controller (although somewhat deritive of other existing things just more balanced), and had an awesome array of third party support. It didn't create or really do anything that particularly impressive as a piece of hardware. CDs were already becoming a thing. If anything the PS2 would probably have a better argument than the PS1 because it achieved infiltration into a massive # of households with packing in a DVD player as well, succeeding in a way merging the video game market with the general media entertainment market
NES >>>>>>>>> all other systems in terms of relevance. 2600 probably behind it. Remember we're talking about significance on the video game market going forward here. Not what system we like the most or what system got into technically the most hands. I don't think it's rocket science.