If that fact is true then its very misleading.
The PS1, PS2 and the NES were all dominant consoles of their generation who came out before their serious rivals. Xbox 360 and the Sega Genesis were also helped by coming out early and allowing them to establish themselves before their respective competiton showed up.
Throwing a bunch of early launching non successful consoles into the mix doesn't change the fact that launching early can be an important advantage. Its just shows that launching early can't be the only thing going for a console in an effort to find success.
Of all the early launching consoles that failed to garner any real support, please name one that you can logically conclude would have done better launching a year or two later.
Imagine if the Dreamcast had launched along with the PS2 or the Xbox and GC. Do you honestly think it would have encoached its current LTD under those scenarios? Launching early helped the Dreamcast, it was just not enough to help Sega overcome its lack of cash.
This.
Early launches previously were trying to get an edge.
Where other consoles failed which launched "first", there were other more pressing reasons for their failure rather than: "haha! You were first, you lose!"
NES - revitalized industry
Master System - too little in comparison to competition
TG16 - decent hardware, not enough dev support by key franchises at the time.
Genesis - great hardware in comparison to competition, key arcade franchises, good dev support
SNES - great hardware in comp, key classic franchises, great dev support
Phillips CDi - weak hardware, muddled marketing message, weak dev support
Pioneer Laserdisc system - interesting/limited hardware, no dev support
3DO - too expensive, ok dev support
Jaguar - not enough marketing & dev support
Saturn - weak hardware, not enough marketing & dev support
PS1 - strong hardware, great dev support, key franchises (FF7 anyone?)
N64 - ok hardware (no CD though which leads to), weak dev support, too little too late
Dreamcast - great hardware, not enough dev & marketing support (EA - not one game)
PS2 - ok hardware, GREAT marketing & dev support
GC - strong hardware, weak dev support
xbox - strong hardware, ok dev support
xb360 - strong hardware, good dev & marketing support
ps3 - strong hardware, GREAT dev & marketing support, too expensive, STRONG brand
Wii - revolutionary interface, weak hardware, weak dev support
Other factors for sure, but these are the main.