Currently, there is little need for high-end PC's for gaming. There are too few games to exploit the investment. Most games from PS4 and XONE are playable with the middle tier hardware.
Further,some games are blocking PC users to make em shine on their righs. Latest example is Watchdogs, which has disabled features which enhance the look of the game, most probably to ensure parity wiht consoles. IMHO, PC gamers should boycott these games and fund projects that will take advantage of their hardware capabilities.
But, to disprove your point, Star Citizen raised over $47 million for a game in the making, which is aimed at high-end PC configurations. Also worth a shout is project CARS.
So, you need to define "niche" in your context. Seeing as most people play some sort of games on mobile devices, we can freely say that console market as a whole is niche.
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