Historically to be honest there isn't room for three consoles that do the same/similar thing.
90s ...
SNES
Genesis
Turbo Grafx 16 (failed)
Playstation
N64
Saturn/Dreamcast (failed)
PS2
XBox (probably would've finished around 30+ million had MS supported it past 2005)
GameCube (failed)
PS4
XBox One
Wii U (failed)
Yes, the X360/PS3/Wii generation had three, but that doesn't really help the point of Nintendo fans who claim three consoles doing the same thing are viable, as the Wii was a full generation behind the PS3/360 in tech and succeeded mostly off a 4-5 year motion gaming fad with casuals.
The general audience doesn't want three different console ecosystems to choose from. They want one usually lead platform, and then another competitive format to keep the market leader in check, and that's basically it. A third platform trying to compete on largely the same merits always gets trounced.